If you're vegetarian in NL it's usually pretty easy, but vegan is another matter.
We were there in June, so it's possible that in July and August things might be different and their restaurant might be open for other meals. But I had checked it out with them prior to booking, and I can speak Dutch.
For breakfast there was fruit, cold cereal and soy milk. There was nothing for lunch nor dinner, which left us traveling by foot or train to the Albert Heijn supermarket in Valkenburg and buying food we could eat cold.
The area is lovely and Limburg is very unlike the rest of Holland. Very hilly, woodsy and tall trees, meandering waterways. Less engineered than the rest of the country. You'll actually need all the gears on your bike if you rent one.
The room was spacious, clean, airy, if a bit out of date. There was a playground on the other side of the river that my young daughter loved. Their yard was beautiful.
But you could almost just as well as stay elsewhere if you're measuring it by food.
Regretfully, I wish we'd liked it more, simply because I felt like veganism had taken a 25-year step backwards. Many fry shops in Holland cook their fries apart from the meat, but not in Limburg. Eating food out of cans because you've nowhere to cook and there isn't a vf restaurant to be found. Not what I'd expected from a vegetarian retreat.
Cons: only a vegan breakfast, no vegan restaurants