Three years ago, cousin phoned. She was planning a party for her twin girls, for their college graduation. She was combining it with a party for her mom's 80th birthday, and THAT was a surprise.

A week later, the twins contacted everyone. (They knew about their graduation party). They were ADDING to all this a surprise 25th Anniversary party for their mom and dad. I told the twins we would be there.

I told my cousin we had other plans!

It was a HOOT! Everyone was surprising everyone else, and folks arrived for the Anniversary party who hadn't been invited to the other parties, throwing a loop for my cousin; the twins had it covered, they planned extra food. We all still marvel about it.

SO: can someone (maybe a few someones, lol) be "busy" on the date Dad wants and have Dad plan Mom's party the date of the party which is already planned and which he does not know about. As for the tickets, can you say you will take care of it and present him with the receipt so he can reimburse you?

Is there anyone who lives close by the 2 of them who can "assist" with the plan, so they don't have WAY TOO MUCH food? And are both parties happening at the home? You need to make sure they don't book TWO Halls! (I'm not sure how large these parties are going to be.)

It will require some subterfuge, but it CAN be done, maybe, if you think on it!