I just checked and we went on 25 Feb which was a Saturday. It was just my sister and I, so no kids with us, as I took her up to SIN with me on a quick 3-night trip. I didn't think the crowds were too bad from memory.
Oh and yes it's very easy to get to. We just took the MRT to Harbourfront Station which comes in underneath the Vivo City shopping mall. From there you can get over to Sentosa in a few ways. The day before we'd been over for me to do some hotel inspections so, that day, we choose to walk across on the Travellator. On the day we did Universal, we just went up to the 3rd level of VivoCity and got on the Sentoa Express which is a little train-like transfer. There is also a free Universal Shuttle Service from the CBD to Universal (must show your passport because its only for foreign tourists). Sentosa Island and Resorts World in particular are well-oiled, slick operators for tourism that's for sure!
Do you know that Universal Studios Singapore is not operated by the U.S. company that runs Orlando and LA? It's run by Resorts World and I think that's one of the reasons it feels different.