I'd throw a big BBQ and just have people over to celebrate. A photographer at the courthouse and everyone puts $ into that. And if do it as close to, if not on the day of adoption.
A friend of mine was adopting a baby and it took 4 yrs to be finalized through the state... And she took her home from the hospital and found out at 1 she was eligible for adoption. So... Sometimes things drag on... And on...
Throw the shower too early and something backfires(a family member appeals) and it'll be awful.