I second get out with the kids loads of great stuff in that site. I wrote about taking babies to festivals a couple of years ago here:[www.festivalkidz.com
Well be going with an 11 month 5yr 8 ur combo this yr
I recommend the tent type travel cot for baby gives you somewhere to contain them too if mobile. Going to switch from airbeds to self inflating mats for the other two this year as the 5 year old always rolls off the air bed we had an inflatable toddler bed when she was younger with a built in cover but she just managed to flip the whole thing as she rolled out
Also second warm baby grow and winter weight baby sleeping bag with shoulders also take a stretchy cardigan you can add as another layer over the sleeping bag.