Exercise is one of those things unfortunately that has to be done whether you are overweight or not. I have included it in my daily routine since high school. I did it while I was in college and while pregnant and now with three boys (ages 1,2 and 3) I do it every day also. Since my kids don't know any different they are fine with it.
My rule is, you (the kids) ask for what you want before I workout (juice, a book, snack whatever) and then you may not bother me while I do it. Sounds harsh but it works for us. Even though they are young they really don't bother me too much. (of course I do have the one year old napping at the time, which helps of course). I've found they've learned to play independently for an hour everyday. Sometimes they'll use the one pound sand weights and do it right along with me too or lie on the floor and do "their version" of ab work.
They've learned also some good cooridation by letting them walk on the treadmill too. (Don't worry I only let them do it when I'm standing on the edges right behind them)
I don't feel bad about it, because they are going to have to do the same thing one day and I think I'm being a good example for them.
As for finding the time, if you work full time also, you probably are going to have to either wake up before dawn, do it at lunch or do it at night when you are exhausted. Unfortunately it really just has to be part of the routine. Its hard, but if you use the two weekend days you only have to do it 3 or 4 weekdays.
I know your house may be really busy but because of your schedule working out at home is probably your best bet. That way you don't have to incl. the travel time. There are tons and tons of different kinds of home workouts and equipment. You may not feel in "the zone" but you can make it work.
Bottom line is, if you really want to do it, you will. Not trying to sound mean but that is really just how it truly works.
Good luck