Sorry to hear about yet another dumb stunt by your STBXH. He is probably feeling too guilty to see the kids much, especially when it's obvious they are on to what a moron he's been. Makes you feel for the kids so much.
About your new last name...that's kind of exciting! All the possibilities! When my D process began I was set to change my name back, but by the time the court date came around I was already moved across the continent and wanted to keep that connection with my son. No one knew us here and I wanted it to be obvious even on paper that I was his mom.
But choosing brand new name, that's pretty cool! How about something Greek? Maybe something really over the top Irish? Or you could do an english translation of Native American, like Runs with Bears or Climbs Mountains.