holy cow, please tell me you don't have 33 kids coming to your house!!!!! That's a party! I'm not familiar with Hello Kitty, so I'm racking my brain for ideas. Plus if you do have a large group it could get messy and expensive. How about felt cat bookmarks? Actually you didn't say you wanted the crafts as a party favor, just something to keep them busy. How about a large banner that they can write birthday wishes on or even a giant card made from poster board? You could also get a blank journal and have each of the kids draw the birthday girl a picture.
If it's outside you could have bubble blowing contests (the biggest, the most, the one last longest, etc.)