More good advice,  Elizabeth.  What I shall do on Monday is call Road Scholar and see what they have to say.   If all I have to do is hand someone $100.00, that might not be an issue...but no sealed envelope with perhaps lots of money.  

And I imagine that these people may be very poor and $100.00 is a  lot of money to them, but who knows who might be watching me do it. 

I'm pretty intrepid--read stupid.   One time when I was in Prague, it was at the end of the Velvet Revolution and the city and the country was a mess.  Everyone was buying black market money....my friends wouldn't do it, but I did.   Not only did I buy black market money, but I went to someone's house with a secret knock on the door and I got my money.   It wasn't an awful lot of money, but maybe a couple of hundred dollars.

I got back to my hotel, where the manager had taken me for dinner and where they all know that my background was Bohemian, and the manager and his secretary took me into their office.   They told me that they had been told that I had been seen buying black market money, and that I better not do it again, or that I could be arrested.
So I didn't buy anymore, of course, .....and that was the Czech Republic...not Cuba.

So...I think that it might not be wise.   You never know who is watching. 
That is the truth.  They might be watching to catch someone and make an example of them.  No, no, no.   The more I think about it, the less I want to do it.