If you get the JR radio with teh DMSS Rx, then yes, you can get a second DMSS Rx to power another plane or heli. However, anything that states "Bind-N-Fly" (BNF) will not work with the JR radio. But you can buy extra Rx's for the larger helicopters and planes.
I myself would go with the DX8. I own is as well as many other members here on the forum. It's one of the best Tx's out there and there is nothing that I have found that you can't do with it. Once you buy a DX8, you will never have to purchase another Tx.
One tip for landing without hitting the tail.
Beginners tend to come back to themselves when landing, which angles the tail down, therefore making it easy to catch the tail fin. To stop this, make sure once you have the heli in a hover ready to land, try to have a very slight, repeat VERY SLIGHT, bit of forward momentum. This puts it in a nose down attitude, keeping the tail higher when touching down.