I walked with my 13 yo from Leon in 2015, and then again (at 14yo) from SJPP in 2016. Walking from Leon took us about 13 days. --- Walking with Ciaran changed our relationship, brought us closer and gave us stories to share. He is now 22 and finishing university, and I am incredibly glad he walked-- and honored that he walked with me.
When my son was about 18, he said to me "I learned on the camino that you can complain as much as you want, but the hill is still there, and you still have to walk up it."
We walked the second time upon my son's request. When he first asked me to go back to the camino, I was dismissive. I'd have to pull him out of school, it was expensive, etc. Then I caught myself-- My 14yo son was asking me to go on pilgrimage with him. This was a once in a life time opportunity for a journey together.
I encourage you to consider a longer walk than from Sarria.
I can think of a few tidbits of practice advice:
- My 13 year old had more energy than I did, he wanted to leave early and walk as far as possible in one day. He was frustrated at my wanting to stop for coffee or look at a museum. So, it would be good to talk this out a bit before hand.
- My son was hungrier than I was. It took me a few days to realize that his grumpiness in the early afternoons arose from lack of calories. He was walking and growing at the same time. We increased time allowed for lunch and also increased the size of lunch. Chocolate with nuts became a staple.
- My son did not hurt like I did. I had blisters and aching feet- and on the first walk, my knee bothered me. He was ready to move out and keep moving. He did not get blisters. He did not ache. He would go for walks after we reached out destination. I increased my amount of motrin, and that (along with the chocolate) decreased my grumpiness.
- We often separated (he walked ahead).
- The three of you might want to go on some practice walks and see how you can pace yourselves. (Though, that will happen on the camino anyway, if you don't get around to it.)