I'm not going to sell our car to friends
Do you have a good reason why you don't want to sell the car to them?
Who the hell are they to me?
Selling something to a friend can be hard. You don't have to sell it to them just because they are your friend. Sell it to whoever you decide is the best buyer.
Fine, I'm going to do what I want.
You can do whatever you want with what you're selling, as long as nothing is illegal and you are not deceiving people. If you are not satisfied with your friend's offers, you can respectfully decline them, but only for the offers and no other reason such as race or any discriminatory beliefs.