My whole family has been active all our lives for the most part. But we all have also went through spells of lack of exercise and/or good eating habits.
My son got off track the worst during his HS years but came back with a vengeance and is in top shape as he begins his military career as a 2nd Lt. in the ARMY.
My wife was never really athletic but was healthy. She was able to get back in shape after both our kids. But like me, we both have been so busy in life and just being their during out kids HS years that she gained some excess weight. She also fell and broke both bones in her leg a couple years back and that made it even worse. But the last year or so she has been working out at the gym and other than some bad eating habits has done well to get back into pretty good shape.
My daughter has been most stable and most active even as she is going through college. But she is lacking in the proper eating department and is now working on that.
I finally got back into it this last January and have lost nearly 35 lbs and am getting back into great shape.
The point is, a family has a tough time doing everything at the same time. It's something to shoot for, but is hard to maintain. We all have our lives, priorities, responsibilities, etc. and so it makes being a complete package hard to do. So do your best to keep everyone healthy and active, but don't be surprised if it doesn't always work. If you built a good foundation though, eventually everyone will get back on track. Keep the faith.