christmas day at the in-laws and we have a club booking on boxing day... cover story help?

so we're hosting his parents in surrey from christmas eve through boxing day morning and we've got a couples-only club thing in london booked for boxing day evening. told MIL we're going to see an old uni mate for drinks. she keeps asking which mate. my husband almost said the wrong name last year and i nearly choked on a brussels sprout. how do you lot keep the stories straight when you're three sherries deep with the family? do you write it down in your phone notes or just commit to one fake person? genuinely starting to think we need a shared google doc of cover stories at this point lol