Race For Your Life, Charlie Brown (1977) is set to be released on February 10, 2015; there will apparently be no bonus features. The Amazon pre-order listing claims the DVD will be widescreen.
The fourth movie, Bon Voyage, Charlie Brown (1980) doesn't have a firm release date yet, but is planned for October 2015. (TVShowsOnDVD.com reports that Paramount says they're delaying until that time in order to tie the release in with the 35th anniversary of the film... which is kind of odd since the film first hit theaters in June 1980.)
The first two Peanuts movies, A Boy Named Charlie Brown (1969) and Snoopy Come Home (1972), have been available on DVD for some time, and will be re-released on February 10, 2015 as well - most likely those will just be re-packagings with no new features.