I love the diaper clutch idea. With a newborn I tended to carry around a big diaper bag, but as my kids got older it was SO much easier to be able to just grab diapers and wipes and head into the bathroom for a quick change. I ended up buying something similar to this: http://www.amazon.com/Ah-Goo-Baby-Diaper-Frenzy/dp/B006OK476S/ref=sr_1_13?ie=UTF8&qid=1425395848&sr=8-13&keywords=diaper+holder
(actually, I bought several because I kept losing them....but that's another story). They were great for holding just a couple of diapers and a travel pack of wipes! Seems like it would be pretty simple to make one.
If they're doing cloth diapers, though, then I think a wet bag would be useful. My understanding from friends who have used cloth diapers is that you need some kind of bag solely for carrying the dirty diapers, until you get home and can soak them.
I also love the handmade blanket idea! Honestly, even if you're just getting to know these people, it means a lot when folks 'step up' for big life changes like this -- I think it helps deepen the connection.