Blizzard Beach and Typhoon Lagoon are both great parks! BB is definitely more of a "thrill park" with Summit Plummit, yet has a really great kiddy area your ds would definitely enjoy. TL has a much more lush, tropical feel with a nice lazy river (actually both parks have this), shark reef you can swim through, a new exciting "roller-coaster" type water slide called the "Crush'n Gusher" but also has fun but slightly less "thrilling" slides. It also has a great wave pool with beach (real waves - you can actually surf in this pool). TL & BB both have a kiddy area, but I think the one at BB is better, IMO. So either way you will have a great time. I guess it kind of depends on how active and adventurous your mom wants to be and what kind of atsmosphere you personally prefer.
hth!