Handsomedan:

 

I think it will largely depend on what you really wany from a bike. 
You could get a short-travel full suspension bike with good anti-squat properties and make the most of being cushioned throughout the vast majority of your ride, or you could get any number of very good trail hardtails, but if you want something like a step-thru frame, or something taht comes with a kickstand, as opposed to a mountain bike that's almost fit-for-purpose, then you'll have a slightly broader search field. 

Personally, I have gone eBike and that's all I'd consider now for something like a Rail Trail, but if that's not your bag you need to write up a bit of a list of what you really want from a bike - not just "front suspension and disc brakes", which I think whould probably be a given for any kind of off-road riding, even if it's just Rail Trail type stuff. 
I'm thinking of things beyond just componentry and weight, but things like ride position, wheel size, tyre & wheel type, rack compatibility etc. 
It all gets quite murky when you go down the rabbit hole. 

Also - how much do you want to spend? That will have a massive impact on your decision making. 

I agree that on the surface a Giant Roam or Marin DSX would fit the general bill, but maybe a dedicated Gravel Bike with flat bars may be better? Lots to consider. 

I love New Bike Day. 

 

I don't have much of an issue with the ride I get now on my old Sirrus with no suspension. So I don't see full suspension being a high priority. Not looking for a step through or kick stand.  

We have talked about the E-Bike option, but while that might be on the cards in the future it's not part of the current plan.

Ride position can generally be altered with handle bar positioning/change of bar, the rest is usually taken care of by getting the sizing correct. Sure there will be variations by make and model but I think it's much like the seating position in a car. You hop in someone elses car and it's not long before you're comfortable with the different position (provided it's not way out of whack compared to what you're used to).

Wheel size is a consideration. All of my bikes have been 27.5". I may find 29" to be what I really want/need though from what I've read it's six of one and half a dozen of the other.

Our bike rack should work with what ever I get.

Yep, the price I want to pay determines the selection. As mentioned above ideally in the $1500 plus or minus range. I don't want to tie up too much cash in this.