If your just trying to find out the gender early 16 weeks is fine but if you want to see the features of the baby I would wait a little, my Dr does them in his office at almost every ultrasound appointment and I got my first at 18 weeks and my most recent one was 26 weeks, I have an appointment next week at 28 weeks. The one I had at 18 weeks the babies looked like skin and bones due to the fact that they haven't really developed any fatty tissue, they look nothing like the ones I got at 26 weeks! They were starting to get chubby cheeks and there features were alot more defined. Can't wait till my next one next week!
It's ok to get it done at 16w. I'm 22w and waiting until I'm around 28w. My doctor says by that time my baby will have her features and body fat.
I just got mine done at 33weeks, most places prefer to do them after 28weeks, the baby smiled, was pouty, pulled her foot into her mouth it was amazing and every feature was completely developed!
Ultrasounds are considered safe as it is non invasive at all. Your baby is still in the stages of developing so I think you should wait out a few more weeks so the baby features are more developed so that you can have a better idea of what he/she will look like at birth.
From what I've heard you should be good! I'm 14 wks and I'm going to get mine at 17 wks only because that's the only date I can otherwise I'd get it sooner! I want to find out the sex already!