We have just done a similar trip, from 9th June to 7th July.
Belgium 1st night on an aire de camping car near Ghent (at Schelde, Gavere next to the river ) which had free toilets and free showers.We stayed here as we wanted to get some California accessories from a VW dealer at Ghent,namely a maxcamp magnetic mossie screen for the sliding door. Next 3 nights were in Luxembourg.
We then travelled down the Wine Route in Alsace, stopping near Ribeauville and Colmar. If you go this route, I highly recomend driving over the Chasseral Pass and upto Col du Chasseral, as long it’s a clear enough day to enjoy the views at the top.Then onto a campsite near Neuchatel in Switzerland followed by 5 nights at Camping Jungfrau.
We bought “ Top of Europe” passes, as recommended by the reception at Camping Jungfrau. We paid extra to get to the top of Jungfrau. There are some great walking routes down from Eiger Station, passing the north face of the Eiger
After Switzerland we spent 6 nights at Lake Annecy, cycle route around the lake is great but there is section where you will have to go onto the road for a few km.I recommend going around the lake clockwise unless you are really decent going up hill on a bike as the road section has an incline both ways, one of which is pretty steep. Annecy is great, we enjoyed market day there.
We came home through Burgandy staying a couple of nights on different campsites along the River Saone , which had a great cycle track. Castel Camping Chateau de L’Eperviere being one of the campsites.