My mum came to our 12 week scan - I invited her as she worked in the hospital where we were having it done. To keep things 'fair' we then invited my MIL to the 20 week scan.

I'm actually really glad we shared it with them, as it's been 25+ years since they had babies, and things had changed so much they were just in awe. It meant also that they asked all the questions of what was on screen etc, so DH and u could listen when we rated, and just focus watching our little one together.