I'm an instructor and I have used all sorts of trainer kites. The Airush 3m isnt bad,
but my favorite is the HQ Beamer 3.6m (best quality, complete with leash with QR, relaunch bridal, fixed loop with QR, video, super nice construction, flys great, nice bag)
I think having a trainer is an excellent idea and it will help you sharpen your kite skills long after the lesson. If you can get a kite before your lesson that will also let you get a whole lot more out of the lesson, although you can still get a good lesson without owning a trainer kite.
I have been doing this for 5+ years and every once in a while I fly my trainer kite just for the fun of it. They are also great if you ever can try snowkiting.
contact Jeff at
www.kitemare.com
tell him I sent you
good luck and be safe. The trainer kite can generate a ton of power, so start in lighter/steadier winds, around 10 knots with a lot of open space down wind, and
do not hook in until you have good kite control. If it starts to pull you too hard just LET GO of the bar immediately (make sure your leash is attached and know how to use the leash QR as well).