I never know if what I suggest has already been thought of, but here we go:
What I've put together for my past bun-sitters:
Each portion of each bun's food in a ziplock back, labeled per bun, and put together all buns per day. (Does that make sense?
I also put aside hay portions, just so I KNOW they're getting enough...also labeled, even though they get the same amounts.
I label on the food container what each bun gets per day so for whatever reason they need the information, it's right there on the source.
I write out what each bun's normal attitude/activity is when feeding, so they can tell if they're acting funny. I also warn them about Maisie's cage/food agression, and inform them to distract her with one of the hay gloves while getting out her food bowl to avoid her noticing you're taking it out and then getting a bite on the hand. Also, I let them know that I hold the food bowl on its sides when putting it back in because she charges and insists on eating NOW (and will bite anything in her way).
Also, I set up a username for them with a simple password, and let everyone here know what it was (the username) and to watch out for them (I also volunteer to watch for your bunsitter).
What else...have the note saying to check for a good pile of poops for each one, and make sure to label each bun's cage so they don't get one confused with another.
I also made explicitely sure they knew NOT to give anybun time outside their cages.
If I think of anything else, I'll put it here...but I also know that you know your buns and your friend...and maybe also try doing a run-through of feeding time with them.
Hugs to you! Have fun!!
Rosie*
P.S. You've probably already thought of it, but also have them call you EVERY NIGHT to let you know how everybun's doing.
Edited to add: Also give a brief outline of a bun's digestive system and how it works (and maybe some articles) about various health issues...along with instructions on how to handle each thing if it comes up. Obviously you won't be able to put down EVERY health issue, but it's worth doing what you can think of. Also, write down regular vet's as well as any emergency 24hr vets near you, and have arrangements with each place as to payment (as well as with your friend).
Also edited to add: I SWEAR this is my last addition...here's the thread I created the last time I went out of town. Let me know if you want me to email you a copy of the typed up (and much more extensive) version of the bunsitter information packet.
http://rabbitsonline.net/view_topic.php?id=28118&forum_id=1