My first thought, as several have said, is a good Goldwing. And even though I'm not a Harley guy, I've run into more than one couple touring long distances two-up on big Harleys. And they are usually comfortably large folks as you profess to be. The huge dealer network throughout this country = huge support network whe you might need service work done.
I had totally forgotten the sidecar option until it was mentioned. One of my friends on here, and someone who rides several different bikes over the past few years (literally as part of his professional photog career) picked up a Victory with a hack and has found it useful and fun. Shoot a PM to GSBS and tell him I sent you searching for opinions.
Also read through the specific forum on here for sidehack info and opinions.