Hi Eli To the best of my knowledge… I think it would be ok for both the medal and the locket to be on the same chain. It’s just a locket, with a photo of your son. Probably ok. It’s not like, putting it with costume jewelry, or something along those lines. :shrug:
My Scapular has both a Crucifix and a St. Benedict Medal attached to it. So, it’s like “3” things, on one cord.
I don’t know if this answers your question. I hope that someone with more knowledge will reply. God bless.