OSX bluetooth private network between 2 macs
Bluetooth is PAINFULLY SLOW… maybe 80-100 KB/s if you're lucky. It really isn't suitable for this sort of use.

Perhaps you could create a network on a host machine, and use a client mac to connect to it for screen sharing. An ethernet connection to the host machine would also allow for internet sharing to both macs (since you'd no longer be connected to your router.)