“(like the DIY elk trip I hope to do in the upcoming years)”

You don’t say how many years BUT… I think you are laboring under a lot of false impressions! For example, longbows are shot differently than recurves; recurves are shot straight up and down and long bows are canted; Spine to bow configuration just to name a few. You say you are “I am really new to traditional archery” so I suggest that you SLOW DOWN. Shoot with your son for a while, like for at least the rest of the summer and just enjoy him and your learning process.

Find a coach if you can or lacking that, read all you can, ask questions here and anywhere else you can and keep shooting what you have. Do not rush into buying a heavier bow for a planned hunt that is a “few years down the road.” As you get closer to that day, you will have more experience and be better able to make a choice that fits you better than just what you THINK you need today. You may even find that your 45# bow is plenty for elk.