For a day trip only, and in December..., I would advise taking the train from Rotterdam to Vlissingen. Two trains/hour, one quicker, takes 1h40m. Then cycle along the boulevard and dunes to Westkapelle if the weather is tolerable, or to Middelburg if it's not. My bike ride on 28 Jan a few years ago:

You wouldn't have to bring a bike, you could rent an "Ov-fiets" (train-and-bike) in Vlissingen for a few euros, that's what I did. Some photos from my trip in great winter weather: flic.kr/s/aHsmX1V81B Westkapelle is where the second part of the allied invasion started, Oct/Nov 1944 [...]

Vlissingen - Westkapelle

Op de OV-fiets, zaterdag 28 januari 2017.