I did a tour a couple years ago with some people that were rather novice at bikes. Seemed like I was adjusting someone's brakes almost every day. And did one major wheel true when a guy put his bike in a bike rack by one wheel with loaded panniers and it fell over. Here would be my recommendations, most of which have already been mentioned:
at least 2 tubes
patches, glue
2 power links for chain
kevlar spoke
1 gear cable (single ended)
1 brake cable (single ended)
spare bolts for attaching the rack
chain lube
zip ties
tire levers
allen wrenches 3, 4, 5 mm and any others to fit your bike
8, 9, 10 mm open-end wrenches if needed
spoke wrench
compact chain tool
Be sure you have the right wrenches for everything on your bike, including the fender and rack connections, and the tiny screws or bolts that center your brakes, and your cleats. Check that not only are the wrenches the right size, but they fit in the right places (multitools sometimes don't) and give you proper leverage. Even though my bike doesn't need any open-end wrenches, I carried one tool with 8, 9, and 10mm wrenches on it and used it many times for other people's bikes.
Oil is good, grease is better.
2007 Peter Mooney w/S&S couplers/Terry Butterfly
1993 Bridgestone MB-3/Avocet O2 Air 40W
1980 Columbus Frame with 1970 Campy parts
1954 Raleigh 3-speed/Brooks B72