We have taken our daughter on three rides using a burley delite trailer and I thoroughly recommend it. A trailer is better than a seat as it allows the children to sleep comfortably, read stories, draw pictures and watch the world go by. If its raining they are dry, if its cold they are warm.
As for the nights, yes they are still full of energy when your tired but we found by cycling hard and getting into camp as quickly as we could as opposed to stopping heaps worked better for all. Em could then run around, go to the parks and burn off all her energy so she slept when we did.
On one occassion BV did flag out an area for families but unfortunately everyone else ignored the flags and camped there anyway and some did get grumpy with the the children chattering first thing in the morning. Despite advising these people that they were camping around children. So you are never going to please those who feel that children should not be brought on these rides. Despite the young age my daughter still talks about the rides and is looking forward to her next. She is four.
So, go for it, but really consider the trailer option. Its also useful for storing extra clothes, rain jackets, spare tyres etc which makes the ride more enjoyable.