We hired four bikes from Josselin at a very reasonable cost of 24 Euros for two hours. The bikes were well maintained. The tow path is wide and even, easy terrain for even young legs, and the scenery beautiful - even the canal locks are beautifully maintained. The only aspect missing was maybe a cafe or two along the way...
Cycled out from Chateaulin towards Nantes. It's beautiful with superbly maintained towpath wide enough for two abreast cycling.
However, we cycled out for around 1.5 hours with no sign of cafe or refreshments along the way.