I've had a request for a birthday cake for a 7-yr old with an artist pallete theme...I did some research and found a few variations...just need a little guidance/opinions...it needs to serve 10-12...I was thinking I could use a 9x13 and cut in in the shape of an artist pallete...should I do one or two layers?  And would that be the right amount of cake?  Once I trim it, not sure how many it would serve....