Depending upon your area... yes!

The reason I say so is that there is a place north of Houston called Old MacDonald's Farm that is packed during the summer, gets field trips from schools during the off season and looks to make a good business of hosting b-day parties.

Do a search in Google for "Old MacDonald's Farm, Humble tx" and you'll find some reference links.

The keys to this are going to be...
- the animals
- the play areas
- the price

Location is important as long as you are near a large population of families and can get the word to them.

Another thing they do towards the end of their season is to have a "pumpkin patch" that brings in many just for the photo ops.

I don't know if the option to get themed cakes would be much of a driver.

Also, unless you have experience, don't neglect to research the costs in the animal upkeep. Nobody wants to put the kids on a pony that looks like it's about to keel over.

Marlin Creek - Idea Seeds
http://marlincreek.com