Well first you need to invite me and I'll bring the fun (since I, too, am only 22 HAHAHAHAHAHAHA).
What a fun party idea. You two should have mathcing birthday cakes or cupcakes. One for people and one for puppies

I just got 2 new doggie treat cookbooks and one of them has a whole chapter on dog parties. You could make a theme and have little take-aways for guests.
I hope you both have a great birthday and a super fun party!