Absolutely take him to the art exhibition! I haven't been there yet (but would love to see the Surrealism exhibit too) but I'm sure there wouldn't be a problem. I've taken my children to many many exhibits, even as energetic toddlers. If he's a baby in a pram, you'll be fine
As for other activities, I think the previous poster is right, he'll just be happy to tag along with the grown ups, though Lange Erlen is a good idea.