Recommendations M5 or other?

My father would like to get back into photography / videography.
He currently has an old 10MP Rebel XTi, 85 1.8, couple of few lenses and some kit lenses.
He would be shooting lots of landscapes, grandkids, video of performances (granddaughter is a buddy singer) and some pets.
Low light shooting helps.
He's a big guy, so he could handle a DSLR, but thinking for lugging around all day etc - the M5 with an adapter may be a good fit for him? Also looking for a Sigma ART 18-35 1.8 for the camera.
Or a Rebel SL2 or something vs an older FF 5DII.
He'd like to stick with Canon and he does print photos quite frequently.
Thanks for any thoughts.

So much depends on your budget but I would lean towards one of the R mount bodies wither the ERO-R or the EOS-RP. The M is a nice camera but Canon just seems more committed to the R mount cameras.

Thanks! That wasn't on my radar - but I think it will be out of his budget.