An answer from a friend who lives in Belgium
I wouldn’t try to get to Dinant and back on a cruise stop. Traffic can be horrendous depending on time of day. It’s really too risky. Trains would be 4 hours each way. So it’s a no from me.
Although not Leffe, there are a couple of breweries in Brugge:
De Halve Maan and Bourgogne des Flandres.
Hope this helps.