If money isn't a concern and the child is thoroughly enjoying it, that's fine. But there's nothing special they do there that you can't do at home, and maybe a lot better since you know your kid better than anyone, especially with so many amazing and FREE resources on the Internet. My 5 year old is nuts about science and there's SO much great stuff that museums and aquariums all over they country have made available online. Right now, he's hooked on the "Ology" pages at (I think) the American Museum of Natural History. Just google for "ology." The Monterey Aquarium also has wonderful stuff for kids, parents and teachers.
Be wary of anything that's too pedantic or academic, because that can often adversely affect their creativity, curiousity and sense of wonder. I think it's far better to let the child do a little open-ended exploring until they find something interesting that really hooks them and then help them find resources to really delve into... whatever it is. (Like mine recently went a little nuts on the topic of bioluminescent deep sea creatures, and with him I learned way more than I ever wanted to know about a truly disturbing creature called the "Angler Fish".)
For younger kids www.starfall.com has great stuff on learning to read. Or mathisfun.com. And there are TONS of links to all kinds of cool stuff from the hoagiesgifted website:
http://www.hoagiesgifted.org/links.htm
Find an interest and google away and maybe you can use that Kumon money for the college fund.
By the way, have you ever used the "Images" option on google? I've used it to find everything from pictures of baby raccoons to medical photos of various skin conditions when my little one woke up at 3am with a bizarre rash and I wanted to know if it was hives or not... Good stuff!