I've got 2 foot tatts, one on each, of my childrens' footprints when they were 3 months old.
They were both VERY painful, and one was swollen for a few days afterwards, but I think as the tattooist was 'old school' he was a bit more brutal than the other one I've been to. I wouldn't say they've faded at all, and look amazing.
I'd definitely have it done, I love foot tatts 
good luck
Natx