There's another option, this place organizes coach bus trips to National Parks and Cities around States.Best is give them a call to find the details. they'll show you the best in the shortest possible time frame
.https://rektraveladventure.com/en/

Thank you all for the wonderful suggestions!! All great destinations that I want to go to now , if not with my parents.

I realized multiple transits may get tiring for them, so now looking for more direct flight routes 😕 either beaches or mountains would be ideal, no car rental

You can easily fly to Miami and visit South Beach, or other destinations in Florida. I like Sarasota as you can combine an interesting area with several things to do as well as visiting the Lido Key beach or Siesta Key or Longboat Key perhaps. Many beach destinations require accss by car such as the Hamptons or Montauk. You can however fly to Newark and make your way to the Jersey Shore to places like Long Branch as a possibility as you don't need to drive anywhere after you arrive as your choice of restaurants in Pier Village.

I was thinking about San Diego. You could stay at one of the resorts around Mission Bay - warm, sheltered water but walkable to the ocean beaches like Mission Beach, or splurge at the iconic Hotel del Coronado. Both areas are very close to the airport. There's a wide range of dining options (accessible by cab or Uber) and if you want a scenic train ride (well, scenic in parts) a day trip via the Pacific Surfliner to fabulous Union Station in Los Angeles (around 2 1/2 hours each way) would be an option. Visit the old Pueblo area of LA including Olvera Street (a 5-minute walk from the station) then back to San Diego.

San Diego would indeed be a fine destination. So much to see and do there. I have been lucky enough over the past 25 years to go there with my husband and stay at the Del Coronado twice for various conferences. I've also gone there on my own business trips but very long time ago.

You all are amazing!

I was looking at San Diego as an option!! But then came across some news articles about beach pollution advisory. Does anyone have any insights on this?

https://www.sdsu.edu/news/2024/02/pu...tion-escalates

Vancouver was also on my list but didn't know if there were enough "nature" things to do + the prices! But will look into it as well.

Miami would be great but not sure if we can tolerate the heat.

The article talks about pollution from Mexico affecting the beaches at the south end of the San Diego Bay area. While potentially terrible, the areas I described (Mission Bay etc.) are at the opposite end of the region and are unlikely to be impacted by pollution from the Tijuana River. If there were health concerns at the time of the visit, the local authorities would take measures to close beaches or issue advisories well in advance of any potential hazards appearing.

As for Vancouver, aside from the hotel price issue (remember you're talking about a short stay) there are few if any North American cities that have better access to "nature" than Vancouver. North of the city, the coast mountains present virtually a wilderness barrier to the urban sprawl. You can catch a shuttle bus to Whistler (sadly, the train service was discontinued) that follows the "Sea to Sky" highway, one of the most scenic drives in North America, and once at Whistler, there are numerous nature activities ranging from hikes to gondolas, boating, etc. Within the city, Stanley Park, one of the world's great city parks, includes old growth forest, lakes and wildlife; marvelous Lynn Canyon Park (a short Uber ride north of the city) offers trails, a suspension bridge over a roaring stream... trust me, there's no shortage of natural wonders.

How is Portland ( Maine) for a 3-4 day trip in Summer? Is it walkable without a car? Is there a good mix of nature, good food and other sightseeing? Would weather be okay (not too hot, no stormy weather, no bugs etc.)?

Portland is great to visit and the Old Port area is walkable as is much of the immediate area, but if you did want to go to a beach or to the lighthouse a car or some kind of vehicle transportation is needed. Maine in general has become a much visited hot destination and so hotels especially in the downtown Old Port area are going to be pricey during July. Because you are by the water, there is always a breeze. I've been there many times but never stayed overnight for that many days/nights as we mostly visit when we are en route to/from Boothbay Harbor or day trips from Ogunquit.