I always give my dragons veggies in the morning and then crickets in the evening. Then they can eat the veggies during the day if they are hungry.
Don't leave the crickets in the cage. It can stress the lizards. It is better to feed your lizards as many crickets as they like to eat in 15 minutes and then remove the crickets. I have spoiled my dragons with handfeeding... some use a separate box/cage for feeding. Maybe that can help?
At my homepage I have written a little about "how to teach your dragons to eat veggies". You can have a look there. SOMETIMES this method helps - but not always. Some dragons are stubborn and don't want to eat their veggies..!
http://www.morion.com/teo/english/experience/frame.html
(Click on "What vegetables" in the left frameborder)
I know some people sprinkle some kind of "fruit juice" at the veggies and that makes the dragons wanna try it.
Good luck!

Vegetables