is this a bad idea?

Cailyn • Welcomed Little Miss Reagan Blakley to the world in May 2016 🎀 our precious Kennedy in January 2018 🎀 and Lady Leighton in January 2022.
A little background, my husband and I tried for 16 long months to get pregnant with our first baby. We underwent numerous test and were referred to fertility specialists due to some of those results-we were told <a href="https://glowing.com/glow-fertility-program">IVF</a> would be our best bet. Well, literally the day before the appointment with the fertility specialist I found out I was pregnant! We now have a beautiful 12 month old baby girl.......and just found out one on the way! We weren't exactly trying the second time around so you can imagine our shock that it happened so quickly and easily this time, especially when you thought your sweet girl was your one and done. 
My sister-in-law and her husband also struggled, much more than my husband and I. They went through 4 rounds of <a href="https://glowing.com/glow-fertility-program">IVF</a> and found out they were pregnant recently (she is 11-12 weeks). Saying my husband's family had big mouths would be the understatement of the year. When we found out we were expecting with our first we told his sister (so she didn't hear from anyone else) first, then his dad, then his mom, said not to share, but everyone knew the next time I saw them. Kind of a bummer but it is what it is. The same thing happened with his sister, only we heard through his dad (we weren't part of the rumor mill is what I am saying). 
Anyways, here is the question, we wanted to share our news on Father's Day (currently, no one knows we are pregnant). I had 2 onesies made on Etsy: one that says, "I'm your (grand)Father's Day Present!" for my daughter to wear, and one that says, "No...I'm your (grand)Father's Day Present! Coming February 2018" which will be wrapped. I will be around 6-7 weeks so it is early but it is family. That isn't the part I am worried about. The part I am worried about is his sister. Is it insensitive of me to share our news so quickly after they found out they were pregnant knowing their struggle (it has been a month and s half since we heard they were pregnant). Should I keep ours under wraps for awhile so she doesn't feel like I am trying to steal her thunder? 
My concern with waiting is that the second biggest understatement of the year would be that my husband's family loves to drink. I have also been known to drink (before I found out I was pregnant with my first - toned it down a lot since becoming a mom. Too scared of a hangover with a baby!!!) so me declining a glass of wine can get heads turning. I have declined a drink a couple weekends in a row now and I am sure they are wondering. I just wanted to be able to share our news myself but I feel like I am being selfish and should wait a few weeks - my husband and his dad are very close so he can't wait to tell his dad on Father's Day and he totally doesn't get my hesitation. Anyways, thoughts?
Sorry for such a long post!!!