Hey comrades. I'm not trying to build a crazy body or get jacked or anything, but I'm getting older and want to ensure I'm not neglecting my body so it keeps up as I go. I've been doing pushups 3x a week (got from being unable to do them on level ground to doing a set of 30, 25, 20 with 5 minute gaps, nothing too crazy) but that's all I'm currently doing. I got dip bars to try and add inverted rows to my routine, so here's my questions:

1. is there a reason I shouldn't just do rows as part of the same 3x a week pushup thing I do?

2. will it be bad if I alternate, assuming I can't do them both the same day, in terms of maintaining a baseline level of fitness?

3. are there very easy/no equipment exercises that do not take much time you would include/add for someone in my situation? My partner and I work alternating shifts, and we have children, so it's not really realistic for me to plan to have even an hour where I can do intense exercise away from the kids/go to the gym, part of why I've been doing basically just pushups is that I can drop and do them while I'm in the same room as the kids without leaving them unmonitored.

I know if I was really committed to building muscle mass I would be doing a bunch of other stuff but I can't devote that kind of time, I'm basically asking for the bare minimum "reasonably healthy" routine.