Vacations with children: a little planning can make all the difference A trip on the train

Last summer I gathered up two of my three preschool children and traveled 3, 653 miles by train - twice! Would I do it again? Definitely! Train travel has much to recommend it, especially if time is not a big factor. For our entire family to make the same trip this summer, train tickets would cost between $430 and $860 less than the lowest air fares available from three major airlines. Children are not confined to their seats as they would be on plane, bus, or car, and no one has the responsibility of being the driver. And travel by rail can provide an opportunity for special close family time.

Here are some practical tips the three of us discovered from our transcontinental journey.

* Luggage. Ordinarily each passenger may check two pieces of luggage (each a maximum of 75 pounds) and bring two carry-on pieces. The carry-ons are the vital ones, for they must hold all clothing, snacks, and activity items to be used en route.

* Clothing. Even during the summer the train tends to be cool, so the children were most comfortable dressed in long pants, short-sleeved shirts, and lightweight jackets or cardigans. We included sweat shirts as well, for mornings and evenings were chilly. One set of shorts each was invaluable when we were temporarily stranded without air conditioning in the 100-degree F. summer sunshine of Minot, N.D.

* Snacks. Food is available in both dining and snack cars, but eating out for three meals each day can be expensive. As passengers are permitted to carry on some food, we found we could plan one meal ''out'' each day and bring sufficient supplies for the two others and snacks.

Foods that traveled well were packaged sliced cheese, hard-boiled eggs, raisins, fruit leather, individual serving-size cans of fruit cocktail, breakfast cereal, and bagels. Peanut butter sandwiches and bagels split and spread with cream cheese were still fresh on the second day when we brought them on frozen.

* Activities. For toys, we brought along puppets, action figures, and miniature vehicles. These kept the children involved and happy in a small area and also acted as community playthings for the spontaneous play groups that formed with other children during various stages of our trip.

All of the trains on which we traveled were equipped with trays that folded down from the seats ahead of us, and this gave each child a small surface area for artwork. We packed colored pencils (they are fewer and cleaner than crayons, and don't break so easily), a small pencil sharpener, blank paper, and coloring books. On one of the trains we were provided with special train activity books which we enjoyed, although they were geared more to older children. Play Doh is another medium that travels well and is easily cleaned up.

On some occasions, more adult interaction was important, and for those times we brought out the stories. At bedtime it was nice to have a few best-loved books from home. Other times new stories were refreshing for all of us. Among the new books bought for the trip were three in which trains were the main characters, and these quickly became favorites. We did not need a great quantity of books, for other children aboard were often willing to share their books when they found an adult willing to read them aloud.

Games were helpful during waiting or tired times, especially one inspired by an old ''Mr. Rogers' Neighborhood'' program. Preparations involved writing a single quiet activity on each of 10 or more index cards. Some possibilities are ''pat your head,'' ''blink your eyes,'' ''whisper 'boo!' '' ''clap your hands,'' ''meow like a kitten,'' ''make a funny face,'' ''wiggle your toes,'' and ''nod your head.'' A die or a small spinner will also be needed. To play, the children take turns picking an activity card and then shaking the die or spinning to determine how many times they (or everyone playing!) must repeat the activity specified on the card.

* Extras. We found that packing some small wrapped surprises for each day was a great way to liven up the few slow times. Any small items - from sugarless gum to decorated shoelaces - can be exciting. And even if the wrapping is no more exotic than brown paper bags, little ones are delighted if they can open the surprises themselves.

It was also very helpful to pack moist towelettes for quick cleanups and to bring disposable plastic spoons and sturdy paper cups along with the food items. Although the trains provided paper cups with the drinking water, supplies were generally depleted by the end of each major segment of the trip.

* Sleeping arrangements. Coach section seats in the trains we rode reclined to a 45-degree angle, and though the children stayed up late and awoke early, they adapted well to the arrangement and slept soundly. We found the best location to be toward the center of the cars, as far as possible from the well-lit automatic doors at either end, for there was traffic all night long.

After traveling the first half of our journey as coach passengers, we were able to exchange our remaining tickets for more expensive ones which allowed us to ride in coach by day, but in roomettes at night. This arrangement is possible on a space-available basis and is less costly than securing a room for the entire time. I slept much more comfortably in the beds than I did on the seats, but the drawback was in having to transfer children and carry-on luggage between sleeping cars and coach cars morning and evening. (In one extreme of this, sleeping cars were being detached from the rest of the train which would carry us to our final destination, and we had to travel 10 train-car lengths, outside the train, without assistance.)

In both coach and sleeping cars it helped us to follow as closely as possible our set bedtime routines from home.

Although each of the trains we rode provided pillows for coach passengers, none offered blankets, so it's a good idea to bring your own along.

The trip we made is one all of us will long remember for the grand diversity of the landscape: the immense expanse of the Great Lakes, the rich green and gold of the cornfields, the huge flat rectangles of grassland under an even bigger sky, enormous angular white and purple mountains arising out of nothing, and the wonderful lush greenery of both northern coasts. We will also treasure the trip for its inner scenery, the sheer pleasure of being together on an unhurried family adventure.