We activate the card for you here in Italy, so that's really not a problem. For the Mega No-Limit option you just need at least 20.01 euros of credit (with 0 credit you cannot use it), so you need to refill the card which is sold with 5? only. I'm not sure if it's possible to refill from Wind's site, but I think so, also with foreign credit cards, but AndreA is the expert of credit cards!
We'll keep you informed!