Travelling to canaries -DS turns 12 whilst there?

[Frenchrugby]

We are meant to be travelling to the canaries this Christmas. DS has their birthday the day after we fly. He will be 12 when returning therefore - and 11 on the way out (very early flight so delays should not cause an issue). Spain now saying that all 12 and over must be fully vaccinated.
Not yet eligible for vaccination at school as under 12 when offered. I know now he will have to have a pcr when returning but does anyone know if turning 12 whilst out there causes an issue?

Should imagine it's the age they are when arriving. They won't stop you travelling home because he's not vaccinated.

Meant to say, this is how I imagine it would be. Would be silly otherwise! Presumably no clear guidance on Spanish govs website?