Depending on who's travelling I would suggest a reservation here:
www.marinabaysands.com/restaurants/ce-la-vi-club-lounge.html#:~:text=C%C3%89%20LA%20VI%20SkyBar%20%26%20Club,in%20Singapore%20%7C%20Marina%20Bay%20Sands
You can go up and have drinks without a reservation but, when you get to marina bay sands you'll see tickets for the sky deck, just to note - that's not the bar, that literally a level below that's an observation deck. So many people make that mistake, head for the bar the views are just stunning and you can't amuse yourself watching the instagram folk on the pool.
Have a quick google of rooftop bars it's the best way to see the city, altitude is the highest in the world I believe, they do really know how to make a city.
Orchard road is worth a stroll, and china town is equally good for a wander.
And in the evenings boat quay and Clarke quay are great for food and they do boat rides around the marine which a good value, you don't need to book these.
The city is safe and clean and you can't really wander to anywhere "bad" I used to live in little India, which was demoed to be an non ex-pat area but I loved it.
There are no Ubers in Singapore just the local taxis and the MRT (underground) is so easy to use.
Have a fab time, oh and don't forget to go to raffles and the long bar for a Singapore sling, it's a bit "touristy" but if you are there it's a great thing to do.