Phuket if you are more relationship oriented... The wife, even kids would enjoy it there. Beautiful beaches, lots of outdoor activities, and helluva inexpensive.
Single guy? Pattaya. Think think, sin city. Still elements that are family friendly there, but for the most part it is a young guy's paradise/ Everything but gambling to be had there. Open air Thai boxing bars are really cool there, keep a couple of Baht in your pocket for tips (it's how they live). Whatever you do, no matter how good a fighter you are, do NOT get in the ring with these fellas. They will let you beat on them for two to three rounds. And then you are done.
Go ahead and rent a car if you are brave (they drive on the left, and they occasionally obey the rules of the road). You will not come close to exceeding your travel expenses limit. I rented one there while we were on Roto 13, and did not exceed my transportation allowance. If you are going to stay mostly stationary (like park in Phuket for the entire time) don't bother with the car rental, as tuk-tuks will get you everywhere you need to go in town for just a couple of Baht.
Make sure you have a camera, because you will have a helluva great time.