I have a problem with blood sugar crashes, too.
Dinner is usually a small thing for me, so I don't have anything to say about that.
If I eat a huge protein laden breakfast that helps me. I also eat every half hour or so on the bike (generally Clif Shot Blox, which for some reason don't make me do the blood sugar roller coaster) and try to eat half a Larabar at rest stops.
I've also found that if I drink a sugary electrolyte mix (Clif lemonade is my current favorite) instead of water that helps keep me on an even keel.
Seems like it's a matter of experimentation and finding what your body likes. Now that I've found something that works for me, I'm very reluctant to change ANYTHING.
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson