Remember I went for a night walk at the beach with another friend around 2am in my previous chalet event at pasir ris. Other then some camp-over-night anglers and a few other couples who won't even be bothered to look at you, there wasn't really other people there except for those packing up at the BBQ pits which I doubt you want it there coz it's brightly lighted. If you go further down, there are many dark and quiet places there, plus, it's by the sea. Even if ppl happen to walk pass and see both of you, they won't be able to make out your faces. Only thing to worry is the weather that night. Not sure about mosquitoes tho which I doubt there will be becoz it's breezy there. Hope that helps