Sunshine Coast is better for retirees in my opinion.. It's more relaxed than the GC as GC is now so congested. You used to be able to go for a Saturday/ Sunday cruise around the GC like a nice drive... Now Saturday/ Sunday is a traffic jam everywhere you go.. I go for my beach walks at 6am - 7:30am in the weekend to avoid the traffic jams.. Its like the GC is a little hole and 500000 people all funnel into it in the weekend so everywhere is busy, traffic is busy etc..
Definitely Runaway Bay, Biggera Waters. Ticks all the boxes.