For their joint birthday party, Rhys and his "girlfriend" Lulu shared a carob/yogurt covered "bone" made of peanut butter and puffed rice. They had a piece of that and a can of Nutro Natural Choice dessert (Lulu had apple torte, Rhys had pumpkin crumble). No complaints from either of them!
Lulu's mommy got the bone from a small doggy boutique not far from our university. I'm sure you can find something like that.
Originally we looked at some websites :
www.funstufffordogs.com
and
http://www.dogbirthdaysandparties.com/
You don't have to buy anything, but you can see some ideas.