1900 park fare: adding a guest at check in

[Disturbia]

Family wanted another day at Epcot (few days before LL booking window which is tomorrow!!!). It’s next to impossible to move any ADRs (We check in 12/21 and this is for 12/27). Best I can do is cancel one of our ADRs (1900 park fare for 5) and book on a resort day for 4 people (found an ADR today for 4; nothing available for 1 or 2 people). Has anyone been able to add a guest or sit at a lounge?