WHETHER YOU AND YOUR CHILD are in the hospital for a day or for much longer, the experience can be trying. Hospitals are noisy bureaucracies that run on a time schedule all their own. For a child, being hospitalized means being separated from parents, brothers, sisters, friends, pets, and the comfort and familiarity of home. However, with a little ingenuity, you can make the most of the facilities, liven up the atmosphere, and even have some fun.