My kids were just thrilled to be told to 'make a mess' with crayons! This would be a great activity to do to keep kids occupied while making dinner, or a simple playgroup activity, since all you need is:
Draw out the letter M, and tell your kids to make a mess all over it!
Hopefully you'll still be able to identify the "M" when they're finished!
Making a mess is part of being a kid - and momstown has some other great ideas to encourage kids to get messy and have fun!