You might want to get your camera out and head to Belgium Pier— just one of the landmarks located 0.5 mi (0.8 km) from central Blankenberge. It's also full of great chocolate shops and restaurants, so you can spend the afternoon having a wander.
Why not try your luck with a visit to Casino Blankenberge during your time in Blankenberge? Make time to visit the spas and churches while you're in the area.