Actually the BW3 character (minus the wings) is a great prototype goal (as far as realism goes) to shoot for... Since that character is most likely computer generated it's probably an unreachable goal but something close may be artistically possible in terms of just a head area...
Per my avatar:
A Bison enclosure is doable as a viewing area only... (unless you want your child to risk losing a hand or more)... Bison are not inherently aggressive but aren't terribly social when it comes to interspecies hands on interactions in close quarters...
Bison are proud, wild animals whose normally slow, deliberate movements hide their athletic ability to jump up to 6 feet vertically, run at speeds up to 35mph and head butt (with horns engaged leverage) a minivan over into its side...
A well constructed, artistically representative mascot head and neck worn by a tall, muscular individual is probably the safest bet for a Bison mascot as long as it truly represents a Bison and Not a cartoon character version of one (per my avatar)...