Skating, whether on ice or with roller blades, is great exercise and lots of fun for kids. Many ice rinks and roller skating parks will rent their facility for a party, or you can take your group and join with kids already there.
If you do go to a public rink, give your guests colorful stocking caps or scarves to wear that will identify them as part of your group. Before turning the kids loose on their skates, tell them you will be judging them for prizes to be awarded at the end of the party.
Baby animals and little kids are made for each other, and if your party will be held in the spring, it is a perfect match. The idea is to expose the children to as many baby animals as possible.
This party is one where each of the children will get to learn one simple magic trick before the party, the children will then have an opportunity to show the guests his trick, after he is done you should follow up their show with the professional magician. Children love magic because the unknown is so much fun. Your child will also have the chance to be proud that he did the trick and that a real magician clapped for him, you will hear about it for a long time to come. Then have the magician say nice words about the performers, how great that would be.