Susan,

I'm currently working on a similar project (sans the children).  For the armature, I wrapped chicken wire around a mannequin and stuffed it with newspaper to help keep the form.  Balancing depends a lot on the pose.  My sculpture is standing up straight and holding a staff, so it's not that difficult for me.  If you can work with metal a little bit, a basic rebar skeleton wouldn't be a bad idea for difficult poses.  And obviously having it attached to a heavy base of some sort is a good idea -- if not necessary.

Hope this helps.

I can't speak for PVA glue, however wallpaper paste seems to do the job pretty quickly.  So far all the pieces of my sculpture that I have finished have dried near completely overnight.

Hi Susan, I don't know if your aware of the work of Philip Cox (U.K) but he creates life size sculptures using cardboard boxes as an armature.
www.philipcox.co.uk  I hope this is of use.
Cheers David Finch.