J.C.
My 2yo daughter and I just went the Science Place and she really had a great time! The downstairs area caters to children up to 7 years old. We were there for two hours which I think was pretty good for a 2yo.
What about a pottery class like Color Me Mine(Frisco) or something similar?
This site may be of assistance...
http://www.discoverdfw.com/attractions.htm