I know somebody asked about this like a couple of months ago (sorry) but I finally found a couple of links for you guys to try if you are interested.
I've made the PB Delight for the Weimaraner's first bday last year and he loved it! Course, I subjected him to vanilla which had corn in it--so watch the ingredients if you have an allergenic dog.
Also, you may consider making meatloaf cupcakes with mashed potato icing (someone on the Weimaraner forum made that and it looked darn good! I wanted some too.)
i think i've made winston one of those cakes... the peanut butter one... i made it for his birthday last year hehe. somteimes i'll bake up a smaller batch and make mini muffins for him if he's been good...theyre nice and come out pretty cake-like if you don't add the carrots.