How about this idea for telling mom.
We send her a beautiful invitation to come to a party - and she will be the guest of honor. This weekend or so.
We can do a few things like :
Siign everyone's names
Tell her to bring her bikini
Ask her to start now to get replacement people to do her tasks for her 'people' !
Count out the days and add that number
I think she willl enjoy something to look at to remind her and for anticipation.