Belgian coast

I would have thought that the obvious place to start is to spend a weekend travelling up and down the coast. You obviously know the kind of place that would suit you. There is a tram service which runs along the whole length so getting from one place to the next is simple.
Knokke-Heist is up-market and expensive.
Zeebrugge is much quieter and a favourite of mine.
Blankenberge is the equivalent of Brighton or Blackpool in the UK or Coney Island in the US.
De Haan is quiet and rather old-fashioned and another favourite of mine.
Oostende is the biggest town on the coast.
From there to De Panne on the French border it is all 'much of a muchness'. Most of the towns are actually inland with xxxx-Bad being on the coast - Nieuwpoort is actually around 4 kms inland from Nieuwpoort-Bad .

It'd be Blankenberge for me. Not because it is the prettiest (De Haan probably is in my opinion), but because it is the buzziest. Really good restaurants, plenty of bars, weird velodrome, pier, a real seaside place.

In addition the railway goes there.

De Haan is a short tram ride away, and just before you get there you'll find a Sunparks. Don't know if you have any kids, but that's be a plus. It might even help you rent it out to friends.

Brugge is easy from there too.