Potty Training Woes Need Help!!!

I have an English Bulldog 5 month old male puppy. He has a great disposition and my husband wants to keep him. However, I am the responsible for taking care of him and I am having an issue with potty training. He knows he is supposed to "go" outside because when I put his leash on him and take him out he goes directly to his "area" and eliminates. The problem is that he doesn't "let me know" when he needs to go out; so if I don't watch him "like a hawk" he will find a place in the house to go. I have 2 small children at home so I don't have the time or the patience to watch his every move. I thought about using a doggie door however, I have yet to find one wide enough to accomodate him when he is full grown. English Bulldogs are very wide and stalky. Any suggestions? I am at the end of my rope!!!