A growing trend among pregnant woman is to have an ultrasound party with their family and friends. It allows them to have a sneak peak of the baby while some are using them to do a gender reveal party. There is some controversy over the idea, worries that the baby could have a problem:
Sills points out that ultrasounds have traditionally been used to diagnose chromosomal disorders, malformations, and to aid in estimating fetal weight or the amount of amniotic fluid -- not for entertainment value.
“Revealing gender has never been a reason to do an ultrasound," she said.
You can read the complete article at: http://www.today.com/moms/ultrasound-parties-new-frontier-pregnancy-over... 
The ultrasounds are done by techs, but not at a doctor's office. They recommend that you have your standard ultrasound at your ob/gyn's beforehand, and will not do any type of diagnosis. According to the article though, that's not to say that they wouldn't strongly recommend that you see your doctor immediately.
When it comes to the gender reveal, I'm not sure I'd want anyone else there if I was worried about gender disappointment. I also wouldn't want anyone to show any type of preference or disappointment if the baby isn't what they were hoping. What do you think?