I showed my sisters weanling once this year, all of our show here in Area II are within 2-4.5 hours drive. Infact, i dont think we have ever driven farther then 4.5 hours for a show in Area II. Congress was only about 5 hours or so, next year will be 4 hours ..i consider us pretty lucky. I dont think its to hard on yearlings really, i think the biggest pain with showing young weanlings would be there dam and trailering the foal/dam safely together ..you almost NEED a box stall in your trailer to do so.
It has to be very stressful showing weanlings, most classes i have seen, its all the handler can do to keep them from flipping over ..if you can. Yes, i would show a weanling BUT i dont see myself hauling a one month old foal off to a show anytime soon.
I'd imagine, if you plan a cross that you may show the resulting foal, you would plan that foal to be an early spring/late winter foal so the foal is older and matured by the time show season rolls around.