Trip to Glacier NP,Yellowstone,NP and Grand Tetons NP need your suggestions

[Where am I]

Well hello fellow road trippers we are new to this site but not to over the road traveling. However, it is our first trip to the subject parks.
My wife and I have two weeks to visit these parks. We live near philadelphia (actually along the delaware river next to washingtons crossing so if you need advise about what to see here both revolutionairy and civil war places we can help). We are retired both 68 I have a few repacement parts so hiking is limited to 6 miles RT per day. I am an avid landscape photographer so maximizing visual delights is a top prioriety.
Our typical routine is to hike in early morning then drive mid day11amish to 3pmish plus minus hours depending on distance to places to see to another location(s).We will also drive during evening to location. We will be staying in motels, BB, motels.

So what we would like to know which airport would be best to fly from Philly to, Salt Lake,Denver,Seattle). We will be doing a loop from that airport.
The goal is to see as much visually beautiful natural resources on the way to and from these parks as possible not requiring off road or traveling dirt roads in poor condition.
We do not care if on the way delights add a day or two coming and going from these parks.
We have beed to Seattle before so Mt Rainer,St Hellens,Olympic.,have been visited but that's it in this area so Seattle is viable depending on visual delights to see on way to the parks.

Could you suggest an airport, and route to travel( it does not matter if we start the loop going to Glacier or the Tetons first, also different routes coming and going is prefered) and sites to see on those routes.I will then look up suggestions,distances time alocation etc. to fill our itineary. thanks for your insights and advise