[Rivière]

I don't see why not. You're grateful for all their help and support and a thank you card is a great way of showing it. Not only that, even if you think they don't remember you, you could always write a bit of blurb in there that kind of lightens the mood - 'You probably don't remember me but I just want to say thank you for....'.

Alternatively, you could contact them beforehand and see how things are to make it a little less awkward in wondering whether or not they remember you.

Either way, I don't see why sending both of them is a bad idea.