Mad great idea to do handprints on canvasses, my steal that one for Xmas for pressies and will remember to put them straight in the bath, Ruby! Did you just use ordinary poster paint?
Ruby My local preschools do loads of events (my DC not there always in local rag!. A few events they have recently done to raise funds which seem to have gone down well are (although how exciting/novel they are I don't know)
Grandparents' Day - a session where grandparent/s came in and shared the session with them, and the lovely crafts were made for them to take home and feel generally loved!
sponsored trike/scooter - each child brought their own and rode round a 'circuit' in carpark until they were tired! They got the local MP in I think who is keen on bike riding. I think.
they are doing a teddy bears' picnic for Children in Need and inviting parents/carers in too - selling cakes and bakes at the same time I think.
Local musicians came in and helped the children to make musical instruments (out of recycled stuff) and then entertained the children.
Loads of brilliant ideas, sounds like you are working hard to make it work!