What to do..What to do..

We are having a tough time deciding what to do for Greyson's 1st birthday. I want it to be big and then again I don't. His birthday is the 25th of August and that is the hottest time of the year. We thought about renting a pavilion at a park, but even in the shade it is miserable out. It's June 14th and already miserable out now. Carlos' boss and his wife have a beautiful home with a large underground pool and we were told that we can have his party at their house. I think that sounds great except for then I don't feel like I can invite all of my friends, just family. I wouldn't feel right having a big party at someone elses house. Let me say that we are pretty close with his boss and his wife. They are very sweet, helpful people all the time. What would you do? I still have about 10 weeks before his birthday but I like to have all my plans early for EVERYTHING. I'm that person who send out invitations like 6 weeks ahead and by the time the event gets here, everyone has already forgotten because I sent them out way too soon! This is Brad and Tina (Carlos' boss and his wife)