Despite the best of intentions, parents may not realize that what they're planning is not necessarily the best thing for their child. What they need to understand is that kids go through certain developmental and social stages where one kind of activity is appropriate and the other is simply beyond or beneath the child's age.
Case in point: Magic! That's my primary expertise, so let's talk about it. Every kid loves magic, right? It's fun, it's mind boggling, and nothing makes people go "Wow!" like a well performed magic routine. Of course, to truly appreciate magic, one has to understand that what they're seeing is actually impossible and defies the laws of science. A 10 year old child can certainly appreciate this, as can an adult. But what about a 3 year old? Can toddlers and young children really appreciate or even understand the performance? Not really. At that age, a child is still learning to process the world around him and accepts much of what he sees on faith. While a toddler may wonder where a coin disappeared to, he won't wonder how it magically disappeared. To him, it will simply be lost. Better to give the younger children something that will stimulate them in other ways, like balloon parties, superhero parties, face painting and such.
The best bet is to simply ask your entertainer what the best options are. Tell them about your group; their age, the numbers, etc... As professional entertainers, we have tons of experience in these matters and can steer you toward the best options for you. That way, your child really will have the best birthday ever!