Keep it simple. One rule of thumb is to invite the number of guests that matches your child's age. Fewer guests can make for a more manageable party and can allow for more meaningful interaction for the ones who are there. Thinking about the needs and personality of your particular child, rather than external pressures of expectations, will help you determine what size the party should be. Minimize and spread out presents.
Presents can be one of the hardest things about birthday parties.
The traditional pile of presents that accrues can be demanding and overwhelming for kids. You can ask guests not to bring presents. You could have your child open the present as soon as each guest arrives and gives it to him. Plan activities which involve the children, rather than entertain them. While children may enjoy these shows, they may also be frightened or overwhelmed by them.