The shows will air on both the mainline network and the PBS Kids subchannel at 7:30 p.m. ET, so if one station isn't carrying it whoever runs PBS Kids will have it available there. No scheduled PBS Kids repeats, and I'm suspecting no mainline PBS repeats. They may not even allow a delayed telecast, but as usual with PBS programs, check local listings.
Also, many PBS stations do pledge drives in early December and I am wondering if stations will be allowed to run pledge breaks around "Charlie Brown Christmas" on Dec. 13. I assume that it's probably too late to secure any Peanuts-related premiums to offer on-air. The pitching would be obvious: "Thanks to public television, your family got to enjoy 'A Charlie Brown Christmas' on free TV once again this year. To make sure that holiday family programs like this one are available free in your home every year, it's time for you to...."