My 18 year old son is on his way from Paris to Istanbul, 10 days from the end. Although he is not 50+ many of his group are.
His blog is here -the spelling and grammer are terrible ( I tried) but the writing is very funny.
Latest pictures are here - most of these are taken by him
You can click through the other photo sections to see earlier pics also
For those interested he is riding a Salsa Fargo with Vittoria hyper Randonneur tires (700x38)
Sounds like a great trip. I have cycled the section from Passau to Vienna, plus elsewhere in Austria, and it was great (except when it rained, as your son found out).