Idea's needed.

I have a very good friend whose sister has 5 boys!!
yep that's right, count 'em 5!!

But as luck would have it, there's finally a girl on the way!!

I really want this to be a special cake, with something along the line of
you finally got it right
or
last but not least
or
Finally a girl at last

I wouldn't say "you finally got it right" because that might make the boys feel bad.

Actually, after that many boys, any pink and girly and fun cake is going to be a big change and a lot of fun for the mom.

My thoughts exactly. I would make the most dainty, feminine cake possible!

I like the "last but not least" one, but I agree with the others about avoiding ssaying the boys are "wrong".
Pink. Lots of pink. Frills, bows, girly stuff all around!!