Contact your
AAA office and find out what tickets they sell and how much. Then compare that price with Universal's price at Universalorlando.com. Also check out the prices at ticketmania.com.
As for your son, both parks have many non-rollercoaster rides that he would probably like.
At Universal Studios, there's Shrek 3-D, Jimmy Neutron, Men-in-Black, Earthquake, Jaws (open seasonally), Terminator 3-D and E.T. Universal Studios also has several entertaining shows too.
At IOA, there's Spiderman, Ripsaw Falls (currently closed for rehab), Popeye & Bluto's Bilge Rat Barges, The Jurassic Park River Ride, The Cat in the Hat ride, Caro-Seuss-el and One Fish, Two Fish, Red Fish, Blue Fish. Also worth seeing at IOA is The Eight Voyage of Sinbad (a show) and Poseidon's Fury. Check out Universal's website that I mentioned above to get a description (as well as some video) of the rides and shows at both parks.