I'd agree. Your first night, if you want to putter, eat and explore the CBD, it would be best to have a hotel in town. There's some hotels on Sentosa Island for a change of pace; if you're near there there's the Cafe Del Mar for drinks, eats at the Seah Im food court near Harbourfront, Food Republic at VivoCity, the restaurants at the St. James Power Station, so many choices.

If you're out late and you're at the Crowne Plaza for both nights, you'll be hit with the 40% after midnight taxi surcharge after the MRT shuts down just before midnight when you decide to head back . Funny how that works...

2nd day, maybe putter around East Coast, take in the park, do mellow stuff before the long haul back. Where is OP's flight going to from SIN?