Either way, I would shoot to leave around 4 - you have to figure just missing a bus (20 minwait), the travel time (15 min), walking time to the gate (5min), a possible wait at bag check(5 min), a possible wait at the gate (5 min) plus walking time back to the restaurant (10 min). Of course you could possibly sail through all of these and be early, but I would rather have to be early and spend some extra time in MK rather than being the stressed out people running through MK a half hour late for your reservations