Legoland is great for kids of that age! Below is a site to show you how to get a deal on tickets to Legoland. Buy one adult ticket a child gets in free. Home Depot promotion.
https://secure4.gatewayticketing.com...ot&c=homedepot
Try the link below for more information on many Orlando attractions.
MouseSavers.com - Your source for Disney discounts, codes & deals!
Also Wonder Works Orlando is great also. All inside and will take the greater part of a day to go through. Discounts are available if you look for them.
Things to do in Orlando | Orlando Attraction |WonderWorks Orlando