I agree. Either pony streamers or a cheer bow. The only difference I would make with the cheer bow is I would use 1 1/2" ribbon instead of a standard 2 1/4". I think at 2 1/4" the ribbon would be too wide. Either way, if they want sparkly bows or streamers, you can always add some sequin material to the ribbon of whichever hair accessory you choose.
I know in the Girl Softball World Series, I have seen lots of BLING on the girls. They tend to like sparkly!