Planning a party for kids is always more stressful than it has to be. There are always those little decisions that either make or break a party, and AmazingMoms.com has some answers and tried-and-true advice:

The Invitation Equation Child’s age + 1 = happy kids. For children under 8 years old, invite as many children as the child’s age plus one. Some parents choose to add 1 or 2 to this equation. Only you 
can know your limits. Of course, as your child gets much older the formula will need revision.

Party Favors In choosing party favors, it’s better to spend more creativity than money. 
Give a wonderful thank you item/items that reflects the party theme; a flowerpot and seeds for a garden party, modeling clay for an art party. 
You can even send the kids home with a treasure they’ve made during the party. The birthday child should hand out the favors. This will remind her to say “thank you”.