The dinner wasn't scheduled for that very night. Monica could vaguely understand Khan's difficulties, so she planned to have that event two days from now.
That period would give Khan and Jenna the time to study the situation and prepare without hindering the eventual programs they had planned before they arrived at the building. It would also allow Martha and Monica to complete the missions they had in mind without risking pissing Luke off.
Of course, Luke was granting the group complete freedom, but his patience was limited, and Monica understood that very well. Manners were an essential part of those relationships, and only soldiers like Khan could partially ignore them since he didn't speak for entire families.
Khan had to admit that he didn't hate the idea of a proper dinner. All his worries had Jenna at their center, but nothing could change her mind. The event was already mandatory, so Khan began to see its positive aspects.