I am looking for a young adult series about children who travel to another land. In the first book, I remember them being able to open a book and it put an umbrella-like blue light around them that protected them from something bad or evil. I remember a tree or building that seemed much smaller from the outside than once they got inside, and a scene in the book where a girl has to walk across a canyon and keep eye contact with someone on the other side. I also remember a scene where they are going through a forest and are told they have to be sure to stay awake and almost fall asleep, but come to and continue on their journey. In another book in the series, a boy is invisible but also frozen or paralyzed and I remember him being stuck on a stair landing. In another one of the books, a boy encounters a man with a map on his leg and I believe he gets to the other land by going through bushes or a hedge. There is a later scene where he is in a boat on a lake full of eels. I have been looking for this series for YEARS so any help is very appreciated.
My best guess is that I read the books between 1993 and 1996. I think I originally checked it out from the church library.