Childhood is the preparation for becoming an adult, do we all agree on this? Good! I think that a child should be involved in the complete experience of redecorating. Design planning to purchase of supplies, preparation of surfaces, painting/wallpapering, and moving furniture back in place. How better can we teach our young the things they will need in life than allow them to experience life first hand? It will give them a sense of accomplishment on a job well done!
Just don’t forget a child’s attention span is limited so don’t get upset when they cant work anymore that day. Keep it interesting (that’s the hardest part) and light! Keep up with light jokes and play, just to keep them (and you) interested in finishing the job!