It sounds like you are doing this trip by yourself. As a brand new rider, there may be a lot that you have not considered. If that is the case, I'd be sure to have spare tubes for each bike (you do need 2 different sizes, right?), the ability to change the tire/tube, tools and wrenches to make adjustments and perform other fixes to each bike. Lights might be a good idea if you encounter a problem that you can't fix and get caught out after dark.

Carry a cell phone, but if you are on rail trails or farther removed from "civilization" be prepared for no signals. And then again, have a plan as to just who you are going to call if you need help. Do you have friends in the area you plan to visit? Broken chain anyone? Broken pedal? Broken leg? Even if you are only doing 5-10 miles rides, stuff happens, and you may be far enough off the beaten path that help is not readily available.

I applaud your enthusiasm but am concerned that being so new to all of this you could leave yorrself open to some unforseen difficulties. We can't plan for every contingency but it does help to have some plans in mind in case stuff happens.