I managed to tickle two of them. The first one said she was ticklish, but had no movement and only giggled when tickling her with my fingertips. The second on didn't laugh, but you could see how she moved her foot and her facial expressions that she hated being tickled with a feather
They were all alright with it to be honest. Told them I am doing a art project and that it requires a picture of the soles of their feet. And that I am sketching feet, and it would be great to do it reacting to being tickled