Too young? We just took kids aged 6, 8, 10, 11, 13, 15, 16 and 17. Nope - 23 is not too young! And if something happens so that you can't go now, I'll tell you we also took an 80-year-old Grandpa, so you have plenty of life left to do this in!
Actually, I think one of the lovely things about the Camino is the intergenerational experience. This is something we make an effort to create in our community at home and we were pleasantly surprised to find it happening in Spain.
Walking without a phone is absolutely A-OK. There's a sense of freedom that comes with being "dis-connected" for a time. Grandpa and my husband both took phones, but we only used them on one day - the day I had to take a daughter with a broken arm to hospital and we did not know where we would meet at the end of the day.
Enjoy your wander.