gender reveal question

Kristi
We went to a third party ultrasound to find the gender of our baby early (18 weeks) she told me she was 98% sure what it was but couldn't get a great picture to confirm it so she wants us to come back on Saturday for another ultrasound but then we have our 20 week ultrasound on the 24. 
The question is, is it safe to have 3 ultrasounds in 3 weeks or should we just wait til the 24 with our doctor?