I’d definitely wait a month or two – it’s a bit of a grim statistic, but something like 20% of pregnancies end in miscarriage in the first 3 months. Although you might want their support if anything goes wrong – everyone’s different.
Hopefully all will go well though! And congratulations!
I’d wait for the first scan, invite the parents around and show them photos and casually include the picture from the ultrasound.
Well, actually, I’d hire a trained stork, get it to casually stroll into the living room, and pass me a note saying, “PREGNANT LOL”.