Just a reminder regarding driving in Germany:
I strongly recommend to be careful with wine testing/drinking when you still intend to drive afterwards !
Although alc level of up to 0.8 promille is "legal" youŽll run into serious trouble already at 0.5 promille in case of an accident !

You might want to use trains and/or local buses between the villages/towns along the river during the day.
The train route from Trier to Koblenz has stops at most towns along the river and buses connect towns/villages without a train stop.
... and carrying a few bottles of wine in a box (or even without a box) in the public (e.g. on the bus/train) doesnŽt raise interest in Germany unless you are clearly below drinking age (16/18) even if youŽd drink wine e.g. on the train - not very stylish but some people do - ...