C.E.
You can get all kinds of party favors, a pinata, decorations at party express (they have both dogs and Littlest Pet Shop!). We've had a bouncy house brought to our home by Awesome bounce - may be difficult in February since you can't predict the weather.
The other things we've done is a party at Build a Bear. They do an amazing job - you don't have to do anything!! It can be from $10/child on up, it's up to you. You can build a bear, just get clothes and accessories for an animal you already have...
If you do the party at your home, you can get each girl a mini-scrapbook, scrapbooking stickers, ribbons, sparkles.. there are kits you can buy pretty inexpensivley. Take pictures of the girls at the party-as they get there, eating cake (or whatever), playing a game.. and have someone print them during the party and they can do a craft of scrapbooking a couple of pages and the cover with pictures of the party - or they could bring pics of themselves, family, pets.. with them to use to save time and ink!
Good luck! Have fun - they grow so darn fast!!! :)
C.