you replied that you have 700 wheels, but what tires do you have on the bike presently and how wide are they? They could be perfectly fine for the trip.
This is something I thought when reading the question. I doubt that I would even consider changing tires for one tour of this length unless the tires were totally unsuitable which they most likely are not. If really wet conditions are expected maybe, but also maybe just postpone.
Now on the other hand it is possible thet the OP lives nearby and expects to do many rides there and wants to have the bike set up specifically for that long term usage.
In any case folks ride that ride with a really broad range of tire choices. Most tires that would be on an LHT are in the range of normal for that ride.