I strongly back @Mike_Cathcart suggestion of Marvel United. It has hit a sweet spot for family time (future step daughters), non-gamer fiance, and super grizzled gamer. It is crazy simple in mechanics, and yet offers solid tactical and resource based puzzles. It moves really fast and pushes cooperation without alpha gaming. It might be one of Eric Lang’s most subtle and elegant designs. Plus, cute Marvel draws the eyes.
Best start is a core set from Target. Then price and options explode. Best add would be to jump into the now ending X-Men KS (less than 24 hrs) to get at least another core plus stretch goal box for lots of bang per buck. The game excels off more since everything can be played together in combination. Unlike other KS games, expansions get opened and played with United.
As @Shieldwolf suggests, Krosmaster Arena is a good one too. That one broke the ice between me and one of the future step daughters so it has a special place in my heart. Start with Krosmaster Jr or a core 2.0 box off Amazon depending on how complex you want to start/ feels right for your daughter.
Between the two, I think Marvel is the better choice. It has opened the door on game and non game experiences; currently both girls have been asking to watch and rewatch Marvel movies together. You can play Marvel United instantly via TTS if you want to try before buy. I did, and I’m glad I did. I’m in super deep now with after market prices, but it’s been an outstanding sweet spot game option. To me, very worth the bridges it’s built along with keeping me engaged as a gamer.
Edit: if you watch reviews of Marvel United, the core box or core only plays tend to be easy and light. There is lots of headroom as you expand. The core box is designed to be the easiest and most accessible entry point. I also think “light” gets misused instead of elegant. It is approachable, yet offers meat. Again, highly rececammed, especially given your specific situation.