Id recommend finding a used one off the classifieds, craigslist, marketplace, etc. See how you like it and get used to it.
Some game & fish departments now have outdoor education centers where you might be able to try them to figure out what you like...
If you're wanting to camp out of it, Id recommend a canoe 15' to 17' long.
If you plan to do a lot of portaging with it, I'd definitely make sure it has a comfortable yoke.
For day trips/no portages, if you're kid is really young (<6 yrs), it might not hurt to have em sit on a bean bag in the middle of the canoe. My dad did that with my siblings & I until we learned balance and not to lean/move too fast. The bean bag would absorb the sudden movements and not rock the canoe.
I've mostly been on lakes in canoes. Very little small river experience. I don't know anything about fiberglass canoes.
My dad had a polyethylene 15' canoe growing up. I'd guess 50-60 lbs and the polymer bottom scratched easily. Never put a hole through it though. No yoke and was a pain to move around solo.
I have a 17', 1970s Alumacraft that weighs 60-65 lbs I found on craigslist. Mine has a good yoke for portaging and loading/unloading. Super comfortable to carry.
I transport mine on top of my pickup cab. I use 4 dense foam pieces to keep it from rubbing. It definitely is a workout, but as a younger guy, that's part of the fun for me.
If I had to make the decision again, I'd still pick aluminum
I also used aluminum canoes similar to mine on a 5 day trip in the boundary waters. Easily had enough space for 2 people per canoe w/ camping & fishing gear. Could fit 3 people per canoe that size, if you didn't have extra gear.