Right now, I have a hard time getting mine out of the house. I have a fourteen year old boy who thinks he should sleep until noon, eat a frozen pizza, take a shower and then start his day. And a thirteen year old girl that has her nose in a book and if you suggest going somewhere wants to do it "when she finishes her book."
They really wanted to go to the local amusement park this summer, but it isn't going to happen because they haven't chosen to make it happen. Tough cookies for them.
I am like you crisi DS12 would rather play on his computer or do something outside in our yard than leave the house. We went to see a movie that he wanted to see and he said he wanted to come right home after it-lol. Maybe because he is an only child he entertains himself well. Good luck to OP I know my neighbor who has 3 kids has the same problems as you in the summer.