You want a public commitment and a ring... you should just admit you want to be married. Now.
It comes across so strongly that you are trying to convince yourself you are fine with this vague future plan. But you are not. And why should you be?
It's quite understandable. You are 37 you have a child, he says he loves you, what would you be waiting for?
The only thing you seem to be waiting for is so your daughter can hand you the rings. Which makes it seem more like you are planning a theater production not a committed life together. The ring handing over would be a brief moment and not half as significant as you imagine.
So you are going to agonise and wait for 4 years so a child can hand over a ring? Tbh that's a ridiculous reason to make such a decision.
Tell him you are ready for marriage now. You want the public commitment and the legal protection because you have a child and you both say you are committed to being together.
Get married. Get it done. You can then plan all the other things for your family: more children, home, education and the future generally.
You are putting this essential core decision on hold for a passingly cute moment in 4 years?
Don't.
Tell him now: you want to start planning a wedding.
See how he responds.
Then you'll have your answer.