Lauren these are quite good photos. I am to trying my hardest at this sort of thing with limited success.
I think the one thing to remember is try and grab face shots rather that backs of heads, its not as easy as it sounds especially if your a little worried of being spotted by the person you are photographing but its great fun trying.
The more you practice the more comfortable you will be with doing it.
Great start there Lauren. And a good choice of B&W conversion for the older couple. Muffin top with tattoos Eh? Probably not the look he was after! - you could probably crop quite a lot of the legs away in that shot (maybe square) to tighten the image a bit. What do you think?