First, congratulations!!! Big news!
That's so cute that Brianna will be excited for this new sibling. She'll be such a good helper. I'm sure Wyatt will adapt especially if Brianna will be around to show him the ropes to accepting a new sibling.
As far as acorns with younger siblings, I'll have to get back to you. I'm due in about a month. The girls will be about 22 months apart. I'll let you know how it goes!

I'm a little nervous!