Hey and welcome to r2r!
When I was around 14 years old I dragged my father into this hobby, at that time we also kept freshwater (planted tanks included) for close to a decade and sure enough, within a year we switched completely to saltwater.
This was 15 years ago and we're still both very much into the hobby, so I definitely encourage you and your son to enter this challenging and addictive hobby
There are many tid bits with keeping a reef tank you need to be aware of, so I highly recommend to take a couple of months to do your homework and nail down the details of early setup and ongoing maintenance.
Look at 2-3 year old builds, see what problems they had and how they managed to handle them, learn about the chemistry that goes into play and so on, it'll tremendously make your entrance easier and more enjoyable.
Also - I didn't see you mention this, and many new reefers don't think it's a big deal, but I highly recommend you to include an ATO.
As for your questions:
- Corals can be very sensitive to containments, thus all equipment that goes into the tank and may contain metals, grease or other unknown chemicals is advised to be verified as being reef safe. This includes pumps, canisters, heaters etc.
- For a tank this size, I don't know if I would bother with a canister filter. My father and I started with a similar sized AIO tank and we were able to keep softies, LPS and SPS with weekly water changes alone.
If an AIO is not an option, a HOB skimmer and filter would be enough and easier to maintain.
Good Luck!
