ok so ive managed to get her to give up anything now performing the exchanges technique and i can go near her when she has food and toys. but the little boy walked past her to get a DVD and she started to growl. Do you think this is because she does not trust hi. Does he also need to perform the exchanges ?
Yes he does, but in light of what's happened recently, I would strongly suggest not yet. It sounds like you are making good progress but taking it slowly will pay off in bucket loads. Don't push her until she is totally comfortable (for a good while) with you making exchanges - it should be totally natural to her and you before you up things a level and get the kids more involved.
Yes it's very likely she doesn't trust your little boy at the moment for all the reasons I've mentioned before - kids are unpredictable, move differently to adults and are, to be frank, quite untrustworthy at times
Kids want instant results and will push dogs and experiment - they are only kids and it's what they do... Jess will know this even from the little time she has spent with you all. It's been a couple of days since she bit him so don't hurry things at the moment. YOU need to manage her at the moment and fully gain her trust, the kids need to take a back seat until things have settled down a bit. Then they can start doing the sort of exercises you have been doing but ONLY while you are supervising and they should still be kept separate at other times until Jess has grown up more and has developed more natural confidence around them.... don't rush things, this is a very long process
She will learn naturally to be OK with them if you let her do it at her own pace and protect her from the children so she feels safe - I am not suggesting your kids are anything but normal kids with this comment, but some pups can't handle 'kids' until they've learnt more about humans and the world in general and from what you've posted, Jess needs to learn to trust you and have a bit of time to feel more secure in herself before you expose her to the kids too much again
Take a breather, concentrate on each good day at a time and most of all, take it slowly and carefully with all of them so everyone gets a chance to relax and gently get to know each other and trust each other over the coming months