I am trying to get my family back on track too. I've been working on a few things right now:
1. Making sure I have good snacks around. This is usually where I get into trouble. I come home from running errands or something and I'm starving and I make bad choices. But if I have lots of fruit and nuts and hummus and veggies around I won't.
2. Planning dinners. I HATE meal planning. I don't know why, but I would much rather just wing it each night. But, I made a new rule: each weekend I make the grocery list for the week and each one of the 4 of us gets to pick a dinner for the upcoming week. DH and I know to pick good, healthy stuff and the 2 big kids (DS3 is only 4mo, he doesn't get to pick yet

) get to look through my cookbooks (all healthy) and cooking mags (Cooking Light, Veg. Times) for ideas. So that's 4 dinners per week and then we fill in the rest of the week with leftovers, and other thrown together meals (big salads, grilled sandwiches, etc.)
3. Making sure we all drink plenty of water. I was really good about it when I was pregnant, but since DS3 was born I haven't been. A lot of times I'll find myself staring into the fridge thinking I need a snack when really I'm just thirsty.
HTH! Good luck with the diet changes and TTC!