I am hoping someone can help me identify a book I have been trying to relocate for decades. There's a catch though: the three details I can remember about it may actually be conflated in my memory from two or even three different books.
For a long time, I had it in my mind that this was one of Madeleine L'Engle's books, but I have read or skimmed most of them and can't find any of these details in her work. I read A Wrinkle in Time in 1970 (I was about seven then), and I read this book afterward, though I think I never finished it for some reason. It could be that a librarian recommended it to me on the basis that I had liked A Wrinkle in Time (very much) and that I might like this book, too.
Whatever this book was, I read it between 1970-1974. Probably before 1972. So it can't be anything written later than 1974, which narrows it down a little.
All the details in my memory involve a group of young people (4-5 of them?), pre-teens or teens, who are about to embark on some fantastic quest or journey (knowingly or unknowingly). As I said above, these details may actually have come from 2-3 different books, but here they are:
Early in the book the characters ride an oldfashioned merry-go-round, and the narrator tries (successfully, I think) to catch the gold ring
One of the characters can set a mental alarm by thumping his/her head against the pillow X number of times before going to sleep and then waking up at that hour the next morning (i.e. seven thumps = 7:00 a.m. wakeup).
In the morning the group gathers in a large room with many large windows, each of which is a portal to somewhere.
As I remember these details, they occur in this order, and I think that's as far as I got in this book(s).
My deepest thanks to anyone who can place any of these memories in a specific book or books!