Actually I am the audience this ad would appear to. In all of my time of shopping for clients if I've ever told another trainer that I was "looking for a children's hunter" no one has EVER asked "do you mean a horse or a pony?". When you say "children's hunter" they will assume you mean the 3 foot division, regardless of whether or not it's a horse or pony, carded or not. A card doesn't mean he shows in the ponies, it just means he can and there won't be any confusion about size. And hey, maybe things are worded differently where you're from. I know lingo changes from place to place. But go to equine.com and type in "childrens hunter". They're all 3' division mounts unless specified "chldrens hunter pony".
You're right, your ad does mention he SCHOOLS 3', not SHOWS 3'. Maybe I should have understood that you meant the pony division from there. But am I missing where it says he shows in the 2' division? Maybe I have. It's been a long day. Also... every show I've been to Bit O Straw's been 2"6.
The USEF rule books says....
"A green pony is a pony not exceed 14.2 hands of any age, in its first year of showing in any class that requires a pony to jump the regulation height or higher for it's respective section. (2"3 for small, 2"6 for medium, 2"9 for large) prior to December first..... etc etc".
Is the Bit o Straw smaller then 2"6 at the shows you go to?
Anyways. None of this really matters. Word your ad the way you want. I'm just saying, you may want to add "pony" in there.