Louis Bonaparte's safest choice during the Hundred Days

How should Louis Bonaparte react to the Hundred Days if the Congress of Vienna retained him as king of the Netherlands?

He should join the Allies against Napoleon, making preservation of his new throne more likely than renewed Bonapartist loyalty.

Keeping Louis Bonaparte would place Napoleon's brother on the Dutch throne just before the Hundred Days. The sensible response would be to join the Allied coalition and distance himself from Napoleon. That choice would confirm the Vienna settlement and maximize his chance of retaining the crown. Siding with his brother would instead risk the throne as soon as Napoleon was defeated.