I've done both biking and touring by car in the area. When on my bike I've ridden the cycling/walking path along the length of the north bank of the Marne river between Epernay and Crouttes-sur-Marne where an e-bike isn't necessary because it's completely flat along the river. There are innumerable champagne houses in the various villages along the river. If you want to explore Avize or Hautevillers or places away from the river by bike then you'll be happy to have an e-bike because the topography rises on both banks of the river (obviously, since the river is in a valley), and often quite steeply, as is the case with Hautvillers. The Epernay tourist office website and other local websites have loads of info about cycling in the region and all kinds of other info useful to tourists (including info about guides/drivers etc.). If you have an e-bike then there are several nearby villages easily accessible from Epernay (Ay, Hautevillers, Cramant, Avize, Oger, etc.). I think an e-bike is a perfectly fine idea and certainly cheaper than a private driver but the choice really comes down to your own preference. Below are links to useful tourist office websites. Be sure to visit the tourist office in Epernay in person as they'll have all kinds of free maps, brochures, pamphlets, booklets etc. and they'll speak English and be happy to answer any questions you may have. Unfortunately their website only appears to have a French version at present but the other TO websites have English versions. If you're like me and you like maps then I highly recommend getting Michelin map #306 Aisne, Ardennes, Marne.
Renting e-bikes in Epernay:
Some Champagne region tourist office websites:
Epernay tourist office website:
The Champagne tourist trail. You may find the French version more comprehensive than the English version:
Hautvillers tourist office:
Ay tourist office:
One of the best websites in regards to all things champagne related: