G.K.
My daughter's 3rd birthday party is actually this coming weekend and we're having a pony party. Renting a pony for an hour is about $100 or so depending on where you get one from but the kids will LOVE it and my daughter is super excited.
Last year we had an amazing luau for her 2nd birthday n that turned out really nice. We dressed the basement to have tiki walls and then our deck turned into an outdoor tiki hut. The adults LOVED it! October is also a good month to have a halloween themed birthday party where the kids can dress up. Another good idea I have stored in my mind is a Carnival theme. Set up some tables in the backyard n have cheap games like shooting a water gun at cups or something.