V.G.
I used to have the same problem, and ironically a lot of people laugh when they hear how I made it work. I would obviously go in with my daughters and then hold them over the urinal portion and they would go in there. It worked great, as long as they didn't poop. My girls didn't like the smell, but they disliked the idea of sitting on a big whole that had a lot of mess in it. As far as the smell goes, you could pick up one of those car deodorizers with you and bring it in with you. I would keep it in it's little package that it comes in until you go into the port a potty. My daughters are now 4 and 5.5, and this year was the first year that I didn't have to go in with them and hold them over the urinal, so you may need to bring a deodorizer with you for a while.