I too have the angled EVO sliders. Kids, wife and I all use them. Great step with this set up.
As for kids slipping through, where they end at the rear door is basically like a little platform where the EVO logo is. When first installed I just told them to be careful. Watched/helped them when they were in flip flops. Now, they've mastered on their own. Like Frank said, they also figured out their own little grab handles and best ways to get in and usually just jump out.
The folding step stool also isn't a bad idea if you need that extra height.