My husband does a two-day MS bike tour every year. He just takes his pump, patch kit, and spare inner tube, as there are plenty of rest stops for food, more than enough really (every 8 kilometers). He only stops at about every third one. They will almost certainly have electrolyte drinks at the rest stops, which saves you having to clean it off your bike the next day. (No bottle seals completely).
As for distance, he does the challenge loops to bring the first day up to 90 kilometers, but rarely rides farther than 40 in training. Mind you, he's retired, so has the ability to do 2 hour rides in the middle of the day on a fairly regular basis. Consistency is probably more important than huge distances at this point.