My dogs are so engaged they won't take care of business when we go outside.

I've been working on engagement with my dogs after watching Michael Ellis' DVD, The Power of Training Dogs with Food. They are all doing wonderfully and I'm very happy with the results. I've run into a small problem and I'm not sure how to resolve it. The dogs are so engaged when we go out for bathroom breaks, that they will not leave me alone long enough to go to the bathroom. I certainly don't want to discourage their intention, do you just not reward until after they've taken care of business?