re 50km per day, especially for the first days and maybe the first week, do extra planning to be able to do shorter days like 50 or 60kms. After a week we all start to get stronger and get into the rhythm of getting up and out in a reasonable time, when to take breaks, eating and drinking properly, all that--and then doing longer distances gradually becomes easier and easier.
sufficient training rides beforehand is so importnat to make sure that bike shorts and bike fit are doing ok, to avoid having physical stuff going on at start of trip that can be sismply avoided by doing enough riding before the trip.
plus if you are in your 20s its one thing, but if in your 60s then its even more important to sort out riding shape etc beforehand.