My family and I have been going to National Parks here in the USA for years. Most are beautiful and well taken care of, with some of them having paved hiking trails so that everyone, no matter their age or health, can also take part in walks and enjoy the parks. Most have wonderful accommodations and you can either go first class or go all natural and rough it.
The Parks have passes that are quite affordable for the whole family, but if you include in your party, your grandparents or members of the family who have a disability -- the passes are rock bottom cheap. That's another reason to go to a National Park. Everyone is accommodated and I approve of that a lot!
Try going to your states' closest National park, even if just for a one day jaunt. NYC has a commercial that says there are 8 just here in town.
Please support the Parks. With Bush's plans for the privatization of National Parks, they might not be here that much longer.
Photo above portrays the Grand Canyon National Park.