Re: Clean up
For the first few weeks with everyone I would use gummy bears as a reward for my 'cleanup crew'...even my 1 year-olds get in on the action. I usually start really young ones (or resisters) with placing a toy in their hand, taking them to the bin and once they throw the toy in I have a piece of Gummy Bear ready. It doesn't take long for everyone to get in on the action.
Re: Time limit to finish food
If they are still actually eating I give them as much time as they need. But, if they are being picky and not eating, the plate goes away as soon as the last one is done eating...and yes, I have sent them to bed hungry. Boy it's hard to see those meals go in the garbage, huh? Trust me, they eat a really big snack when they wake. They can be stubborn little monkeys. Best of luck!