@the_elete - Hey, thanks for posting those example pix.
You should be aware that printing on canvas just sucks up detail in images, so you would likely need files that are at least 3000 or 4000 pixels on the long dimension to get nice sharp, decent sized canvas prints. Since the ones you posted are, at most, several hundred pixels on either side, and artificially up-rez'ing doesn't generate any new information, these are going to come out either very soft or, if artificially up-rez'ed / sharpened, they will clearly look "artificial".
Maybe, because these are memory / memorial pix, being soft is not a big deal, but if you want them sharp, check to see if these are the largest size you have, ie, the largest pixel dimensions? At such small pixel dimensions, even making a nice sharp 4" x 6" drug store print from these would be getting questionable. If they are scans of old prints, then, I would suggest looking for the negatives and having those scanned, or, if digital, mounting a search for the original digital files, or, failing that, re-scanning the prints at a higher ppi value (aka, "resolution").
Also, FYI, printing on canvas can be difficult, I *strongly* suggest getting some smaller test canvas prints made before you commit to purchasing large canvas prints.
I would also suggest that because the backgrounds in all of these pix is busy and sharp, you have whomever is doing these for you to use effects to draw attention towards the actual subject(s) and away from the background. Below is a 2 minute example of one of the zillions of possible ways to do this, including both lightening or darkening the background, lowering contrast and/or saturation of the bkgnd, vignette and other edge efx, etc.
HTH,
Tom M