You can walk, hike, bike, do low impact aerobic exercise, yoga
(carefully - certain positions you'll want to avoid), tai chi, swim, light weight training, etc. You'll probably be told not to lift anything heavier than 20 or 30 pounds, and to be careful to avoid falls. After my hip surgeries, I think my toughest task was to remember not to cross my legs at the knee. :)
When and if you have children, that'll be a bridge you cross when you come to it.