This probably won't be a 'popular' position--but IMO, a dwarf miniature horse should NEVER be 'used' in a public display, no matter HOW good the cause. Why? Because the general public is just NOT going to recognize the health issues and problems of dwarfism; when they see one on public display, they see 'cute', not much else-no matter what they are told. In an educational forum locally-say, a 4H club meeting or the like-where the dwarf could be CONTRASTED with a healthy miniature without disabling physical issues-then, perhaps--but otherwise, NEVER.
Additionally, I believe it is unkind to virtually ANY horse to subject it to an overage of public display/access. I have yet to meet a horse that didn't get SICK of it when it had to endure too much of such 'access'. It is human nature,and understandable, for people to want to touch;still, most horses get VERY tired of this, esp. when it comes from strangers, after a time-and understandably so. EVEN horses that are 'kept away' from actual physical contact from the 'public(such as those who are shown extensively, or travel as exhibitions-i.e., some of the big-name multiple hitches) can suffer from defensive,aggrevated responses-wouldn't you, if you were shut in a small space with a lot of noise and worse, constant physical contact from strangers? I used to take miniatures up to our State Fair and just lead them around, for people to see and enjoy...I was ALWAYS with them, and careful to supervise--but after a time-an hour or so at most-of 'being out and about', it was time to return to their (secluded, where the 'public' didn't usually roam) stalls, and exchange horses! A 'little' of this kind of public exposure can actually be beneficial to a horse's overall acceptance of the world around it, but a 'lot' has SERIOUS drawbacks to the horse, in my experience.
Margo