For my daughter's 5th birthday, we did a pony party.
We had cowboy hats, bandana's, sheriff badges, water guns, candy and stickers for party gifts. Her cake was a horse that matched her plates, a brown horse with sunflowers and we had other sunflower decorations. We also of course had pony rides. The littler children enjoyed the water guns and hats, it was great, the kids rode for about an hour and a half, then we opened presents and ate cake and ice cream. I have an ice cream tip as well, buy the ice cream in cups, it makes for easy clean-up.