I just wanted to report that my taco bar was a huge success! Thank you everybody for your suggestions.
Hmmmmm -- I followed your recipe for the chicken. It was divine and I will do this again. Thank you!
SamiHami -- the grapes coated with goat cheese and pistachio was a huge hit. A nice refreshing appetizer to cool the palate with the spicy salsa/guac, etc.
Amara -- Thanks for the suggestion of black olives. Several guests commented "Wow! There's olives! So yummy, I love olives."
Zilla -- You mentioned grilling the steaks for a char, so I cubed small pieces, marinated them and then put the pieces under the broiler for a couple of minutes. The broiler grill/char was a very nice touch. Thanks!
The mishap that I had was with the beans. Apparently I need a new crock-pot. Sigh. I soaked the beans over night, put them in the crock-pot on high at 6 a.m. Seven hours later, they were still crunchy! So I tried to salvage them by putting a bunch into a large sauce pan with extra broth to boil for a bit.
Did not work. Especially because I forgot about them.
I hope I can salvage my really, really, really burnt sauce pan.

But everything else was wonderful!

Thank you all for your help and suggestions.