He would love the Marvel comics section.
Where should we stay on the Disney property? Would We be able to do Disney and Islands of Adventure in three days?
That depends what you're looking for. There are some Disney hotels for 100-something per night and some for 500-something per night. Do you want a restaurant in there or do you want to take the kids to Downtown Disney for the rainforest cafe and places like that for dinner? I could tell you some that are more kid friendly than others.
There are pros and cons to staying at a Disney hotel, and then would you want to stay there for the 3rd day even though you'll be at Adventure Island? If not, maybe instead you just get an Orlando/Kissimmee hotel for all 3 days. Lots of hotels have shuttles to theme parks.
You can do both in 3 days, I'd say 2 says at Magic Kingdom and 1 at Islands of Adventure. Magic Kingdom could take more or less time, it really depends on what you're doing there and how involved you are i.e. All the rides, all the character meet and greets, all the shows, but I think 2 is good.