Deb
I can appreciate your concerns.
My new little Victorian place is brick, with plastered walls. So drilling holes into the walls for my framed artworks was a SERIOUS business & meant that I should be very sure of
where I wanted each picture to hang, perhaps permanently (or at least semi-permanently).
The best advice I can offer is don't hang the blighters unless you are pretty sure you want them in particular spots for quite a while. If this means waiting till after new furniture is bought, etc., well so be it. Better than having your walls riddled with unwanted holes all over the place, requiring mending.
Curbing my own impatience was not easy. Undersatement! But I'm glad I did, because I changed my mind about the placements MANY times, as I got used to the place & bought new furniture & fittings. As well, I've had to have the previous holes (from the previous owner) repaired. (For some reason all his stuff was hung incredibly high.) If I'd added to these without properly thinking it through it would have created a big mess to fix.
A suggestion: Why not invite the 2 chaps around for drinks & nibblies & discuss all the ramifications of the potential work with them?