Ahh it's a pain hey! I was going to suggest limiting snacks and eating early, but 5:30 isn't that late really!

Some of my other tricks are to eat the dinner meal at lunch time, or (probably a bad habit in the long run) to sit them in front of a movie/tv while eating (I set up little ikea stools as tables and have little chairs) - then they're not focussed on the food and it gets eaten while they're entranced. That's usually a trick for if they haven't eaten much all day.

But yeah really, mine tend to eat the most at breakfast, moderately at lunch, and then seem least hungry at dinner time. Crazy kids!