If you have three different sizes, I suspect that you also have at least three different date codes.
Making a big, long trip, you definitely want a good set of tires.....guessing they are ok is just taking a big chance.
I think if it was me, I would purchase a complete new set and if you have sufficient storage, keep the best tire (of the same size as the new ones) for a spare.
Most large MH's don't have spares due to the fact that the average person is not physically able to handle not only the weight of the tire/wheel, but also the capability to remove the lug nuts or to torque them down to 450 ftlbs.
I would bet that 95% of large mh owners just have an emergency roadside assistance insurance (Good Sam, Coach Net, etc) and just have them bring a new tire (at your expense) to you when you have a blow out.
In addition to having good tires, a TPMS is almost a necessity.
Good luck
Ron