Advice! My husband is leaving for 9 weeks!

Okay so my husband is leaving for basic training for 9 weeks. Ill be 15 weeks when he leaves. We are considering going to a private ultrasound place to see if we can get the gender of our baby before he leaves so he doesnt have to find out via snail mail. So my question is... have any of you found out the gender that early and had it be accurate? Had it be wrong? Its only a 50 dollars to get it done privately which we dont mind paying my concern is that they either wont be able to tell because its early or theyll tell us its a girl and then when i go at 20 weeks theyll see we actually have a boy! Lol and i dont want to have to correct any family we told and so on. Anyone been in a similar situation or saw the gender this early id love your advice!