If you should find yourself in Belgium with an Alpacka looking for a fairly casual river trip I would recommend the Semois, near the border with France. It’s class II max, mostly class one, but through some very pretty country. It has the advantage of snaking more than any river I’ve ever seen which means that 5km of walking can give you an easy 15km of rafting back. Plus it’s full of fish.
The last time we did it, we rafted into the town of Boullion which has a really cool castle perched right over the river. It’s an impressive sight from the water.