1. The Don Rodenbaugh Natatorium in Allen is AWESOME for birthday parties!!! It's perfect for December too since it is indoors with a mini lazy river and water slides. I think it cost around $5 per child to go and if you want to rent the party room...it's only like $20/per hour. I would suggest going there and taking a tour. Or you can also Google it (Google Images)and view some pics of it since they don't have many photos on their website.
2. The Indoor Safari Park is also good for bithday parties for that age. There is one in Plano and I think one in Frisco or Dallas too. They have a mini train and robotic animals for the kids to ride on. There is also mini golf and lots of bounce houses. The price is reasonable too...around $7 per child to get in and not much to rent the party room.
Link: http://www.indoorsafaripark.com/
3. We once used the outdoor Pole Barn pavilion at Meyers Park for the venue of a surpirse party. It's a really pretty setting, right beside a lake with a bridge. The outdoor pavilion has restrooms, a stage area, and about 10 picnic tables....so lots of room! The best part is that it only cost $20 to sent it for 4 hours!!! However, there is a $75 deposit that you will get back via mail once the event is over. You could always do his party there (weather permitting) and even do an early gift exchange at his party. Just a thought.
Good luck! I am sure he will have fun no matter what!