Agree with Stoppit.
Along with exercise, diet also plays a role. If your eating habits are unhealthy, you could make some changes in that area…implement healthier cooking habits, curb the junk food, etc. It’s not going to be effective if you do the work out and then gain all the calories you worked off by eating an unhealthy meal.
Exercise together. Join a gym…or go for a walk/jog in your spare time (evenings or weekends). Maybe get some exercising equipment for the home. At least your husband has the awareness that he needs to get back in shape…it would be tougher if he was complacent and defensive about the matter.
I can understand that it’s easier said than done, but try to adopt a little flexibility…because as you grow older it requires more work to stay in shape…stress can lead to weight gain…various health problems and even medications can cause it…you yourself might find it harder to get back into shape after having kids. These are some things that you may go through in the future…and should be considered. This is not to invalidate the importance of maintaining yourself physically.