I just always accept that Bayon will be very crowded. That still doesn't detract from the amazement of the place. Bayon is usually a place I like to visit early and then work my way northwards on foot through the other temples. In the north east of Ankor Thom are some smaller temples that very few people think to visit. Those are good for a more relaxing time. I personally don't like to eat on holy sites, but if you don't share that sentiment, then that's where I'd be looking to have a quiet picnic.