The Support for the Cuban People OFAC reason for travel specifically mentions supporting independent Cuban entrepreneurs (cuentapropistas), like owners of casas particulares, by giving them your business as a part of a "full-time" schedule of support. The point is to foster an understanding that the capitalist system works, even in Cuba.
OFAC regs mention NOTHING about employees of hotels owned by the government in partnership with a foreign entity (as most are) qualifying under support from US based travelers..
So yes, it is a moral issue, and in the (unlikely) event that an audit were done on any traveler in future, possibly a legal one.
As I said before, Cuba is unique. If your primary preoccupation is your own
comfort on a tropical vacation, over contact with the Cuban culture, find another island that will cater to you.
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Guides:
"four nights in Havana and two in Vinales"
There are lots of guides to take you around Havana, although you can just as well jump in a taxi to wherever yo need to go or walk to many places. There are regular taxis or classic car tours/rides.Try Strawberry Tours for free walking tours (tip the guide afterwards) in the historic neighborhood(s) and some other paid tours. Get yourself a good guidebook at home. I recommend "300 Reasons to Love Havana" to start with, to decide your priorities. ( )
As far as getting to and from Vinales, that is another advantage of staying in a casa. The owner will undoubtedly have a friendly taxi driver in mind, who can get you there at a reasonable price. Your casa owner in Vinales can arrange for the return trip. Most classic cars are not so comfortable, but some have been done over very well, have air conditioning, and would hold 2 couples and luggage comfortably on such a trip (several hours). You can ask to stop at Las Terrazes for lunch and a swim in the river on the way. Or there is a bus.
You don't have to be fluent in Spanish to get around. Cuba is also very safe, so you don't need a pseudo-bodyguard either. Some people like to have their hands held though. Not at all a necessity however.
And yes, maybe a taxi driver from Havana also has to ask for directions to a certain address of a casa in Vinales. No big deal.