Any advice would be greatly appreciated”
A day trip to Giethoorn from Antwerp?! Did you even check how long it will take to get there? From Antwerp you will first need to take a train to Steenwijk, which will take 3,5 hours, followed by a 15 minute bus ride. Your return trip from Giethoorn to Brussels will be even longer, because Brussels is further south from Giethoorn.
You asked for advice, so here is mine; don’t do this.
Most helpful advice thank you :-)