If it stays fairly windy there in Colorado Springs you will probably do better skipping the traditional trainer and going with what most companys call an advanced trainer. It's always windy in Texas, especially by the lake where my club is. So we really love the Hobbico Avistar. It's a semi-symmetrical wing but it's loaded lightly. It slows down very well, handles the wind well (for a trainer anyway) and is very predictable. If you want a straight up shopping list, here it is:

Hobbico Avistar plane
Thunder Tiger .46 PRO engine (IMO, skip the bushing engines like the OS LA series. You'll probably want to use this engine on your next plane, and the extra power will be welcome)
Radio set- At least 6 channel, computerized, 2.4ghz from one of these 4 manufacturers: Futaba, Hitec, Airtronics, Spektrum/JR (talk to your instructor to see which brand he can buddy box with)
6v flight battery 1000-2000 mah NiCd and appropriate charger (see "optionals")
Props, 4 way glow plug wrench, and spinner- 11x6 works with the .46 PRO just fine, but check the manual if you buy a different engine
Standard ball bearing servos (I'm a fan of the Hitec HS425 or Futaba S3004)
a servo extension for the ailerons

Box of rubber bands for the wing
Fuel- Omega 10% works great, or Powermaster if they have it
Electric starter and self-contained glow driver (I really prefer attaching the starter battery to the starter, but plenty of people do fine with a 12v lead battery and a cord)
Field box (doesn't have to be one from your hobby shop, but you do need something to put your sundries in. I use a plastic tool box from Walmart)
Hand tools, CA glue, exacto knife and blades, and every kind of fastener your plane uses (it really stinks to not be able to fly because a 5 cent screw vibrated out and you can't find it)

Optional (get these if you can afford them now or borrow them if you can) Covering iron and heat gun for fixing covering, a computerized charger for fast charging and cycle testing batteries (this has saved me two planes since I bought my first one), prop balancer (I love the DuBro one because you can also balance your spinners with it), a radio case big enough to also put your charger in

As you can see, this stuff adds up. If you want to be able to fly at the same time as your son, you obviously don't need all the field gear twice, but you will need everything in the first group per plane. You might consider buying one trainer for you both to use so you can "spot" for each other between flights. There is actually a learning benefit from watching another person learn while you watch, because the observer soaks in the instruction without the stress of flying at the same time. You also can see each other's mistakes and learn from them. Then when you son solos (90% likely he will before you) put your money into an Ugly Stick or similar plane to do sport flying with. But I can heartily recommend the Avistar as a primary trainer. I've watched it myself on windy days when the traditional flat bottom trainers are all over the place and stressing out the students the Avistars are flying smooth circuits and doing great. Over the 5 years I've been an instructor and hearing the experience of guys who have instructed for twice that, the students who fly Avistars learn faster and solo faster than anyone else simply because the plane is so obedient.