You say you feel you
ought to spend more time with the kid. Perhaps you
want to spend more time with the kid, and actually you don't want to be uptown so often.
If that's the case, tell your partner that.
In your situation, I'd want to see more of the 16 year old. Your partner may say, "Well, it's not like we ever see them even when we're at home." And, yeah, you can't get teenagers to hang out with you all evening, really, but just to get them to sit down for dinner is good, and valuable.
In two years, that kid'll be gone.
Another thing I noticed with teenagers. If you ask them if they mind something - "You don't mind being on your own at home, do you?" - you'll often get "No, it's cool. You go.." But they don't always mean it, and you don't find out till much later. "You used to leave me on my own for days. I hated that. It was like you weren't interested in me."
(That conversation isn't verbatim. But you get the point - which is that teenagers often tell you what they think you want to hear. And mine have certainly done that in other circumstances.)