Survivingslowly, does your 12 year old hate all rides or coasters?
Disney has lots of rides that are not coasters, in fact most aren't.
There are shows, parades, character meet and greets.
Something your 12 year old and other kids might enjoy is looking for Hidden Mickey's.
If it is your first time, go to City Hall on entering Magic Kingdom and get First Time Visitor oins. Also available in each of the parks (ask at guest services)