In my family, when we're not out on a family fitness adventure, Tom and I are swapping training time while the other parent is on kid duty. This may be the most practical way to get in exercise, but it isn't always the most fun.
Thanks to a holiday weekend in the presence of my extended family, my husband and I actually ran together this weekend while our niece had a tea party with our girls. As soon as we saw that tea set come out and heard that juice and cookies would be served, we ran.
Now, my husband and I don't run the same pace. I have to run fast and he has to slow down, but it works out. We get to talk, to not talk, and when we're done, we're both psyched to have our exercise completed. And our kids got plenty of exercise, too, without us -- playing ball, riding bikes, walking, and running with their older cousins.