My DF is a bit the same, he doesn't like going walking and I practically have to beg him to come out with us. makes me feel a bit sad sometimes when on the weekends while I'm out with DD walking the dog that there are mums and dads out and about with their kids.

Are there any nice parks or walking tracks in your area? Or just nice spots for sightseeing? What are the tourist attractions like in your area (i.e. any museums)? Do they have any hobbies you could all do together, or if not find one. Maybe gently coax them into playing with a ball with your DD at a park instead?

As for getting them out there, maybe suggest to meet at a place, rather than either of your houses so you dont have a battle trying to get them out of the house. Say something like 'we were thinking/wanting to do such and such this weekend, why dont we all go together'. Much better than sitting at home, and good for you to get out and experience some different things! I hope you have better luck than i do motivating Df