Need some ideas....
 

Of places to go for a week with family, end of August, 5 adults, 1 toddler and 1 infant. Parents of toddler and infant do NOT want to sit still at a beach house or all-inclusive. They were suggesting Cuba, which I nixed due to weather among other things. So, it has to be someplace that isn't wildly hot and humid, that has things to do including hiking and specifically kid-oriented things, that has some quaint and/or historic towns, etc. Can be anywhere that's "doable" from the west and east coasts of the US for a week.

How about New Hampshire or Vermont? Look in any of the ski areas that have other things going on. It's a small enough ares so you could be in the mountains, historic area, lakes, etc.

Your topic title doesn't exactly show what you want. Try re-posting with more info to catch the eye.

Agree with NH area. In North Conway there's an amusement park meant for children, specifically toddlers, called Storyland. Hiking and day trips for the adults.

Niagara Falls, Canada... Fly into Buffalo airport... stay at the Falls... nature, history, attractions, Wineries, good food, big people and little people stuff...

Eastern Canada (which would include everything from toronto/Niagara Falls east) is definitely on my list of possibilities (as is Western Canada!).

Hmmm.... How about http://www.blackbutteranch.com/. Or https://www.destinationhotels.com/sunriver-resort.

You could meet in the middle, in Denver. Go to Devil's Thumb Ranch for the week.

It has something for everyone.

Lodging prices vary, from cabins to lodge rooms to bunkhouse rooms. All are very nice.
Food there is great. Service is spectacular. Scenery is unbeatable. Weather in August will be awesome. Horses, cows and other farm animals. Kids' activities. Hiking, zip-lining, fishing, biking. . ..

Easy day-trip to Grand Lake, or even Steamboat if you want to spend more time in the car.

You won't be sorry!

http://www.devilsthumbranch.com

Forgot: pool & spa