I don't screen my movies by rating, but I often find the ones I watch are PG or PG-13.
Just make your kids watch Red Dawn every day!
Really though, you might try a service like Blockbuster Online or Netflix, you can probably search the titles by rating and they have thousands. That may help.
There are allegedly video rental clubs that offer edited movies with the sex/profanity taken out, but they were the subject of some copyright suits a while back and they may not be around anywhere.
I have also heard of online services specializing in family-friendly movies, but couldn't find one in a simple online search. Maybe I'm not Googling the right terms.
You could always ask people at your church, if you go, or at your kid's various activities if they know of anyplace.
Hope all of this helps.