Is it strictly a "lawn", meaning it's basically just a single type of grass? If so, how is that accomplished, and who is doing the work to make it that way??
Maybe you could convince them to ease up or stop altogether on any treatment/cutting routines they are doing...just to start letting some other things take
root to give it a bit more diversity...where I'm at it doesn't take long for some dandelion, clover, plantain, smart weed (among others) to start to grow along with the grass. Yes, weeds.
After some things like that start to come along maybe the mowing routine could continue to be scaled back a bit, like every other week or more...and only doing select areas. Around my yard I've been practicing this for several years and I feel much better because a lot of these "weeds" actually flower and the variety of insects I see among them are proof
enough to me that it's the right way instead of intensive manicure.
It's kind of like the STUN way (Sheer Total Utter Neglect) but more like the SUN way because a little cutting and weed pulling here and there keeps things in check just enough to still look good (in my lousy opinion lol ;) and bee useful.
If they hardly spend anytime there, maybe they can just call in a mow right before they arrive? That way in the idle time it at least was more nature/wildlife friendly, and it will come back after they leave and let it go a bit again.
Just some random thoughts...not sure on how far away it is, but maybe you could be the one who does the work to it so you can do it your way!
If they have lots of $ then try convincing them to hire a natural minded landscape company (or again, do it yourself!) to make more beds instead of lawn...simply bringing in lots of dirt,
wood chips, brush piles, etc. and getting someone smart to figure the proper plants that will work together for a low/no maintenance system.