Spacebag is a good idea.

I would take a bucket for the dirty nappies. Wetbags stink, unless you plan on washing every day. You could then use the bucket to chuck your stash in in the car for the initial travelling. But then.. you need somewhere to keep the stash once you need the bucket. hmm... go the space bags Just be careful packing it into the car.. they tear really easily I found. Perhaps space bag them so that you can fit a lot into a suitcase or something.