We stayed near a place called Volendam in North Holland and did a fantastic bike trip, along a causeway to an island, then catching a ferry back to the mainland, stopping in Edam to buy cheese..... Cycle paths all the way, priority at road junctions, flat surfaces, excellent signposting; honestly, it was brilliant. We only did a day's ride, but it would have been perfectly possible to do more.
It was perfectly feasible to cycle from there into Amsterdam, although we decided to drive in because I wasn't convinced I eanted the DCs cycling in a city.
We've done this twice, and it was great both times! The first time we took our own bikes (Dutch ones, natch) with us, and went on the ferry from Harwich to Hook of Holland. We then spent 10 days cycling in a big loop, including stops in Delft, Utrecht, Amsterdam, Alkmaar, Haarlem, the Hague and probably some other places that I've forgotten. Because we stayed longer in Amsterdam, we averaged 30 or 40 km on the days we were actually travelling, which was perfect: short enough to be done in half a day (and still have time for sightseeing when we arrived) but long enough to get from place to place. We mostly stayed with private families through an organisation called Vrienden op de Fiets, who at the time charged a maximum of €17 pppn and are happy to put up both you and your bicycle.
The second time, we did stay in one place (well two, actually) and hired bikes for day trips while we were there. We spent a week in the east and a week on the north coast, both in holiday parks run by www.landal.nl. They're like less posh versions of Center Parcs and because we booked at the last minute we got them for a couple of hundred Euros per week (although this was about 5 years ago).
Both holidays were great and I'd do it again like a shot, even though we were just a couple then and now have 1 (soon to be 2) DC. The Netherlands is brilliant for cycling for lots of reasons: flat, tolerant of cyclists, huge network of cycle paths, compact country so towns v close together. It also seemed to be pretty family friendly, from what I saw. And best of all, you can eat cheese and waffles all day
True, you do have to pack light! It also sounds as if Mercedes' DD wouldn't be happy to do longish trips in a single day, too. But we did do a stay-in-one-place-and-do-day-trips holiday the second time we went, and I'd recommend that just as much
Do you want to be based actually in a town/city or just near one? Lots of Dutch cities are quite small anyway and they tend to be quite close together so you might be able to get to a couple if you're based somewhere in between. Do you want to be on the coast or inland? Coastal areas can be quite hard work cycling because they're so flat and windy, but they're fun in other ways. Keukenhof gardens are lovely in the spring (billions of tulips!) . We stayed once in the East (in one of the Landal sites I mentioned earlier), which was great - we were basically in the middle of a big forest, which had loads of long and short bike trails for exploring the area, but we were also only a mile outside the nearest town, so could pootle over there for shops and cafes. Our site had and outdoor pool, but it wasn't as swish as a hotel one would be, so I guess you'd need to be based somewhere quite big for sometging like that.
you could book through canvas holidays to stay in duinrell,waasanar, we payed 300ish for a week including return ferrie from harwich to the hook ( could do hull to Rotterdam) it's a cheap centre parks type holiday, has a theme park and swimming complex if you don't want to bike every day.
Close by the Hague and scheveningen, has excellent bike paths nearby, as does the rest of the Netherlands