dd-wrt - 801.11b,g --WiFi transmission distance--?

I help maintain a wireless network (home with a few outbuildings) and have a potentially odd request. I'd like to slow down the network. If someone on the network opens say Hulu, or Netflix it does a quick speed check and streams at the highest/HD rate. I'd like 2-3 people to be able to stream at say 1mbps. I only want to offer 2-3mbps at the highest so people can't tie up the network.

So- It's a DD-WRT Linksys with v24.

In "Wireless, Advanced Wireless". I have turned basic rate to "1-2mbps" (the network is at "mixed") and the transmission rate is at "auto". I then run a speed test and it's around 10mbps. Mission not accomplished.

Q - If I turn down the transmission rate to say 11 or at 5.5 the speed obviously goes down but then my signal doesn't go as far right? Isn't that essentially 802.11b? And G goes farther right?

While I want to slow down the speed I don't want to lose the coverage. Any ideas? I don't think there is a right and wrong answer. I know if I went "dd-wrt pro" I could slow it down per mac address but I just want to do it across the board.