I am thinking since it seems to have a great beefy flavor to just play off that with some sea salt, cracked pepper and maybe a little cayenne to add spice.
Probably go with a solid Medium rare -> Medium to satisfy most. I am sure we'll have a few in the crowd that request well done. I guess they can eat chicken.

Any other easy suggestions? Remember this is for a large crowd and not in my kitchen so the difficulty needs to be pretty low, even though we have a pretty elaborate tailgate.