It's hard to plan a trip when you are unsure of the distance. First, make sure the bikes are in top condition then just carry a multi tool, patch kit and pump, maybe a spare tube or two.. A bivy sack for sleeping under the stars.
Light weight clothing and a poncho. Enough money for the laundromat, food and emergencies. Maps. As far as carrying the gear goes, you could use back-packs but that could get very uncomfortable.
A rack and panniers is the best way. If none of the bikes has eyelets to attach a rack you can buy a rack that clamps to the seatpost. I used one of these as well as a front rack that adapts to the front fork without eyelets. I did a trip to Lake Placid in the Adirondacks from western NY, over 300 miles in three days.
We had no budget constraints so we stayed in hotels. Ate well, slept well and relaxed in pools after long days in the saddle.
Try and keep the weight of your gear under 30 lbs. Remember to eat enough when you are riding, you will be burning 600 or more calories per hour while riding and those calories need to be replaced as you go. Shoot for 70% carbs and 30% protien. A huge breakfest works great to start the day. Four eggs, bacon, homefries, toast and juice.
Don't forget a camera.....