I think it'll be fine if they're pretty well-behaved kids. Just have them line up and maybe pet the horse one at a time... and don't be afraid to pull her away if she acts nervous. I mean you know the horse better than any of us, so I think you can make the judgement ;)
Good luck! Sounds like lots of fun!
I remember when I was in 1st grade someone's uncle played Pawnee Bill at a rodeo/show and he brought his horse (Named "Y" lol) and we all got to ride and we got a horse shoe :) I still have the shoe, and the memory!
Every great dream begins with a dreamer. Always remember, you have within you the strength, the patience, and the passion to reach for the stars to change the world. ~Harriet Tubman