I am a white adoptive mother of a black child. I used to do foster care, and I attended a workshop somewhat like this twice. This was focused just on hair & skin care, not on culture as well. That is a lot to fit in to one workshop!!
I am a hair person, so I really enjoyed learning the basics and wanted to keep learning more. I ended up teaching myself, which wasn't hard once I'd gotten the info from the workshop, and I've enjoyed braiding my kids' hair & taking care of it over the years.
Non-black people tend to be afraid of black hair. The presenters were cheerful & used humor and friendliness to break the ice. They passed around a number of products, discussed washing & moisturizing and styling, and lotions for skin. They talked about older children needing to have more complex styles to fit in at school, and our county's foster care actually paid for stylists visits for kids for this reason. I seem to be highly unusual to want to do it myself - most inexperienced people are very intimidated.
Having a couple AA toddlers or young kids around to let people touch their hair (respectfully & curiously) to get a feel for it and to point out if it's healthy or not and how you can tell, and to demonstrate a braid or two and let other people try it is great. In our case, it was just a couple kids who were already being fostered by some of the participants.
Book recommendations are great - they told us about Happy to be Nappy and some other more instructive books. I'd maybe point people to the Curly Girl website - it's white-dominated and therefore probably a more comfortable place for white people to get info & advice but there are also black people there talking about their hair and the types of hair discussed include types that are more common on AA people. My partner has a "Jew-fro" (she's white & Jewish and her hair is extremely curly) and loves the advice there, which is similar to how I style the AA kids' hair.
Well, so I think I'm probably responding after you've already given the workshop, cuz I'm not here all that often, but maybe you'll do it again in the future and maybe this will be a little helpful?
Thanks for doing this - you're doing the foster parents and teh foster kids a great service!!