FYI - there is a school of thought that eschews carrying extra coolant and advocates carrying plain tap water instead.
The theory is that our rigs are small making space and weight carrying capacity precious commodities. Water has many uses; coolant only one. If one needs to add water during a trip the minerals in the added water will do no harm in the short term and if it is a serious cooling system failure the coolant is likely to be drained and replaced upon the return home thus preventing any long term negative effects. Also, did you know that plain water is actually better at cooling than ethylene glycol?
Don't overthink preparation for your trip. Making modifications right before a trip sometimes causes more problems unless there is time to work out any bugs. Just be sure that maintenance is up to date, all fluids are fresh and topped off, your belts and hoses are in good shape, charging system working, lights working, brakes adjusted and in good repair, tires in good shape and balanced and aligned, fresh wiper blades, all known mechanical problems repaired. AAA membership is a good thing too, but don't wait to the last minute to get one because there is a hold on tow privileges for brand new members.
Have a safe trip.
