Praslin and La Digue are definitely worth it but as everyone else has said it very much depends on how you like to travel and what you want to get out of the trip. If you're only spending one night on La Digue spend the first day at Anse Source d'argent because it's at its best in the late afternoon when all the day trippers have left. There are other beaches on La Digue but that's the one people seem to be interested in with limited time. Praslin is a very decent size so you can visit different beaches, do some walks, take a boat trip etc

If you like walking then you'll be able to fill a 5 night stay on Labriz as there are two decent walks that will fill a couple of days.

I don't know if the boats are running more frequently again but for the journey back to the mainland you're probably much better off flying, unless you have lots of luggage, as the flights are so regular.

Bob