Thanks for the tip, I ended up doing just this. I bought the “Would you rather” and the “X-Rated” expansion packs… Instead of mixing everything up though, I shuffled the packs and left them in their own unique pile, then assigned a number on a dice to each… 1/4 for original, 2/5 for Would you rather, 3/6 for X-Rated… then on each turn we would roll a dice and then pick a card from the pile dictated by the dice.
It worked really well, and I just made up a little “board” with placeholders for the decks, and a reminder which numbers were assigned to which deck.