Supplies for expresso/cappucino/coffee maker?

My in-laws requested one of these 3-in-1 machines for Christmas. I found one and purchased it, but now I'm wondering what supplies I should pick up so they can make drinks on Christmas morning if they'd like.

I'm a huge coffee fan, but I have no idea about the others.

Any suggestions for a few items I can pick up to go with it? Thanks in advance!