I would have to see the boat in person to be sure, but I suspect what you are suggesting might be overkill. If there is no evidence internally or externally of damage on one side of the canoe, I patch all the way across the hull is probably more than you need.
You should be able to tell just by looking the extent of any damage to the structural fabric on the interior. It is possible that gel coat is hiding some structural damage to the fabric on the exterior, however. It also appears that you have some loosely attached gel coat at the area of damage.
I would start by chipping away any gel coat at the area of exterior damage that is loosely attached. You could use something like the blade of a utility knife to do this. I would not necessarily try to remove all of the gel coat that is spider cracked. I have gel-coated composite canoes that have had spider cracks for decades and the gel coat has not come off nor has there been any evidence of damage to the structural fabric beneath the spider-cracked areas.
If upon removing the loose gel coat you see evidence of broken or delaminated fiberglass fibers, keep removing the gel coat by chipping it off or sanding it off until you have uncovered the full extent of the damaged fiberglass. I would then apply an external patch of fiberglass to any apparent areas of damage.
I would also closely examine the exterior surface of the canoe opposite the crack in the center rib. If the exterior surface looks undamaged, I think you could get away with simply patching over the internal crack. And I would definitely patch over the side wall/chine crack on the interior surface even if you don’t find any evidence of damage to the fabric on the external surface.
Unless there is evidence of damage all the way from the side wall crack to the center rib, I probably would patch each area separately simply to save weight, materials, and epoxy. As long as your patches overlap onto perfectly intact hull by 2-3 inches, your repair should be perfectly sound.
If you need to buy new fiberglass cloth, I would suggest getting 6 ounce/square yard S fiberglass which you can get from Sweet Composites. Be aware that fiberglass cloth has sizing that helps the fibers absorb resin evenly. If your cloth is old, the sizing may have deteriorated or the cloth may have taken up atmospheric moisture so it might be best to start with fresh fabric. As an alternative, you could use 5 ounce/square yard Kevlar fabric for the interior patches, also available from Sweet Composites.
You can find a bunch of youtube videos on how to do simple gel coat repairs. The color match won’t be perfect but on a white boat, the repair shouldn’t be too noticeable.