OP, I don't get the reason why you think you need to sell your car.
You only have a 120 volt outlet (NOT 110)!!!!!!! in the garage? So we have these guys called electricians, see? Call one and get a 14-30 or 14-50 put in. Or at least a 6-20.
You've decided to start a family? So what? Kids are small, they'll fit in the back, and by the time they are 2 or 3 they'll be clambering into the back seat all by themselves. Why should you give up your dream of a car you like for some kids who will only whine, scream, cry, make messes, cost you money, and ultimately probably disappoint you? Do you want to look at them years later and think "I gave up my new Model 3 for YOU?"? I wouldn't even consider that if my wife were pregnant, I'm far too selfish and self-centered.
Keep your 3 until the Y is in volume production, then if you still think you need a Y, trade the 3 for a Y. Getting rid of the 3 now for a different car so you can buy a Y later makes absolutely no sense.
I have a 23 year old nephew who has got to be one of the biggest dumbasses on the planet, he clearly gets it from his dad. He was ok up until around 15 or so, then it's been all downhill from there. He doesn't listen to my solid life experience and advice at all, and boy am I glad I never gave up anything to give him a chance. Except some cash to buy him a beater Plymouth Neon because no one else could afford to get him a car. 6 months and 2 wrecks later, it was junked. My main thought was on what my hard earned cash had gone for and been wasted on, and this bonehead seemed to not care at all.