Salmagundi was an unknown dish to me until I encountered it in Countess Constance Wachtmeister's Practical Vegetarian Cookery. While hers is a bit plain, it is pleasant, easy to prepare, and almost certainly sure to be eaten by children. It would also be easy to make something more exotic using the same formula.
Peel (if necessary), chop in strips, and boil in salted water until softened:
3 small potatoes
1 large beet
1/2 of a small cauliflower
I boiled the beets separately to keep from coloring the other vegetables. Run under cool water, and chill. Arrange the vegetables over lettuce leaves, and top with a chopped cucumber pickle and a chopped tomato. Pour a mayonnaise dressing over everything. (I used some Vegenaise thinned with lemon juice.) The Countess suggests serving with crackers and cheese. I did't have any vegan cheese on hand, but we ate it with crackers, and the crunchy contrast was nice.