You may be pleasantly surprised with the weather. We have been going in February for several years, and with the exception of 2 years ago, were able to swim several days on our trip.
You could do mini-golf. We like Winter Summerland.
Downtown Disney is fun to walk around. There is lots there to keep kids entertained too. The
Lego store has a playground that kids can play in. There is the big
Disney Store and a toy store. The theming is great and the restaurants are terrific.
The Boardwalk area is fun at night time. You can rent surrey bikes and pedal around the boardwalk. Kids generally like that.
There are also the Pirates Adventure for kids at the Grand Floridian and Boardwalk area. But you would probably need reservations for that.
Resort hopping is great. We like to visit the different shops at the resorts and have lunch. At AK Lodge you can even see some of the animals.
Fort Wilderness I believe has horseback riding and carriage rides.
Tons of options and never enough time.
Hope this gives you some ideas.
Have a great trip!