1) Some of the kids in the neighborhood (Marcy, Jake, and Bernadette) owe their sense of security to an older couple living at the end of the block, the Barnwells. I changed this sentence in several ways. I replace "most" with "some", because there are only three children listed as "most" and the number does not agree with word choice. I also put the children's names in parentheses, which I find more fluid than the dash. I also changed the order of the "Barnwells" and the description of them as an "older couple" as I find that the opposite way is wordy and a run-on sentence.
2) The children find them so not just because Mrs. Barnwell takes the time to help them with their homework whenever their parents are at work.
I changed this sentence and added a subject because it was a fragmented sentence without one as originally written.
3) The children also feel a sense of security due to the Birdwell's because of several other reasons: Saturdays in the park, snacks Mr. Barnwell makes once in a while in the late afternoon, and the woodworking projects they encourage the kids to start that are sometimes visible in their front yard.
I changed this sentence in several ways. Once again a subject was added to the original because it was a fragment as written. Further, the lengthy listing of reasons was set-off by a colon in order to make the sentence easier to read and less clumsy in structure. "Start" replaced "begin" to keep the correct tense.