Go Kellee!
Go Kellee!
Go Kellee GO!

(waves pom poms furiously but leaves out jump splits part)

we're all cheering for you hon!

(and hoping the MIL presence or non-presence will be resolved so you don't have to deal with that as well)

just think how nice it will be for Charlie to have a playmate, he won't be losing you, he'll be gaining a brother. But to be sure, there will be lots of adjustments for your family.