Speaking of eating crabs in SG, some may suggest Long Beach, Jumbo or No Signboard typically for sitting comfort and ambiance consideration, in my opinion. If you don't mind to eat in a place that has no air con, then I'd suggest Eng Seng because you paid less for more, comparing to other name brand restaurants.
1. They serve AT LEAST two crabs for each order; therefore, it's better to have a larger group to go there. However, if you're crabs lover, then two of you are okey too, like me =P.
2. During Fri or Sat evening, please call them in advance to reserve your crabs, although you still need to queer up waiting for your table. No table reservation can be made; thus, just get there as early as 5pm. Don't be surprised if you see a full house there at 5pm on Sat.
After dinner, then you could walk across the street to have the "King of all fruits", the durians.