The Avenue Verte is really lovely. You have to ride on the road a bit to get to it, but drivers in France are so much more considerate. Once on it, it's lovely. Ex-railway, so virtually flat. Tarmac like ironed silk. There are places where it crosses little back roads and you are meant to give way, but in my experience (ridden it twice now), there is virtually no traffic on these roads, so with a good look each way, you can generally just ride across, and the 'barriers' at these points, which in the UK would be just wide enough for the tyre and one pedal, are hardly barriers at all - we were all on recumbent trikes and had no problem at all getting through.
There is at least one little cafe/ice cream hut on the route, but you can also detour off into villages along the way to find a cafe/tabac for coffee or orangina.
If you're riding it at the weekend, it'll be heaving with cyclists, families, walkers, rollerbladers etc - so expect to take it easy and say "bonjour!" a lot.
If you go to the end (or at least where it ended two years ago when I last did it, it's about 30 miles (I think), and pitches up at Forges les Eaux, where we stayed in a perfectly nice good value Logis hotel. Can't remember the name.
Beyond the Avenue, in the direction of Paris, I don't know, as we were heading south. But my experience of riding on quiet back roads suggests that most of it will be lovely. Drivers really do take care and pass wide, and the only hoots you get tend to be 'hello!' hoots. I imagine if you have kids with you, they'll wave and shout 'Allez!' and so on.