We went to the Kawuneeche Visitor Center and consulted one of the rangers. We explained to him that we were going to Idaho Springs and we would be happy for one more trip to the park. He sent us to Adams Falls, on the other side of Grand Lake.
Although the falls are not between the main entrance gates of Estes Park and Grand Lake, they are still inside the national park, and you need a ticket and a time slot to enter. The problem is that you can't purchase them onsite - online, and there is a lousy cellular connection over there. So it would be better to buy the Park Access and the Time slot in advance.
Somehow we managed to buy Park Access and time entry, and we entered. Read here about purchasing tickets and coordinating times for Rocky Mountain Park.
The route is circular and one and a half kilometers long. Some climbs are on the way, but overall, it is easy. In the middle of the route is a beautiful view of the falls.
Charming and beautiful track.