Yay! Just reserved the park shelter we are using for Rob's birthday party! It has a nice playground and splash pad and we are doing an ocean-y theme because of the splash pad, mainly whales I think (for my gigantic boy).
Here's the park:
And here are the invitations I like:

Edit: I found another one I think I like better than the first 2, and it's cheaper and comes with a free thank you card:
Re: Birthday Planning! (updated)
We are renting out our community clubhouse and pool area so we are doing a luau theme. Not my favorite theme, but the kids birthdays are only 2 day