There are people who don't like birthdays, having let a fear of wrinkles and the decrepitudes of age interfere with a natural delight in receiving presents. Or worse, perhaps they are the victims of Childhood Birthday Trauma -- struggling through the early years as the one child in the classroom who never got invited to a birthday party, or the one child who never was given a party.

Birthdays are for the people who own them and since, in later years, the birthday owner may decide to conceal his possession, feeling that the acquisition of another tie is not worth being publicly proclaimed 50, it is particularly important that childhood birthdays are happy ones. It takes very little to make the day a special one and Meredith Brokaw, who owns Penny Whistle Toys in New York City, has come forward with ideas to aid the celebration. With Annie Gilbar, she has written The Pennywhistle Party Planner (Weidenfeld & Nicholson, New York, $12.95), a book that gives general and quite sound advice on giving children's parties. The authors also suggest specific parties, complete with checklists, time schedules, party games, menus and recipes that would calm the most hysterical parent and can be bent or ignored by those of a more relaxed nature.

Most thoughtfully, the authors have included send-away sources for items that may not be easily obtained locally. There are one or two ideas that seem to be reaching too far -- only a parent who loves punishment would choose to give not only a birthday party, but a half-birthday party six months later -- but the book obviously is written by people who have partied often with the younger set.

Children's parties, they point out, should be tightly organized; let children and events wander freely and the result will be chaos. Although older children may not mind waiting till the end of the afternoon to open their presents, small children can't bear it. Even small children who are not receiving the presents get edgy. One 6-year-old was close to despair when three hours had gone by and the gift she had chosen for the birthday child was still unopened, one of many in a tantalizing heap.

Brokaw and Gilbar suggest that with younger children, gifts should be opened as they are presented. There also should be things for children to do as soon as they arrive. Most of the guests have been waiting for hours for the party to start and if, upon arrival, they must wait still longer, they'll get bored and mischievous. This is not an age group that can while away an hour with pre-party talk.

The parties should not run too long -- the authors suggest that two hours is ideal for younger children and three hours for the older set. They also mention something many parents don't think of: When buying or making favors for the guests, provide one for the birthday child as well. Favors should not be elaborate and expensive. The child giving the party is a good judge of what the others would like.

The child should be involved in every stage of planning the party, from guest list to menu to games. It not only tailors the day to fit, but the preparation prolongs the enjoyment of the birthday.

Since children are always interested in themselves, the authors recommend that the parent use a Polaroid camera to provide pictures for the small guests to take home. They tell of parents who have used pictures to good advantage -- like the woman who asked the other parents to send photographs of the invited youngsters and pasted the pictures onto boxes holding party favors. When the children arrived, they saw a pyramid of pictures and, choosing their own, found their favor.

Polaroids were used by another parent as a way to show the small ones where to sit at the birthday table. Someone took a picture of each child as he entered and then placed the photographs around the table; when it came time for ice cream and cake, the child found his place by finding his photo.

The authors also caution that the party should fit the child. A parent who becomes enamored of an elaborate theme that has nothing to do with the child's tastes or interests is forgetting who the party is for.