Hi fellow Minnesotan!
We just got back from the 1/24 Eastern (i've started my trip report on that board if you're interested!) We didn't bring a memo board but I did bring a Post-It note pack which we left on the dresser near the door, along with a pen. We told the kids to leave a note if they were changing location, etc. Worked great. We took the two-way radios and never used them. They were kind of obnoxious IMHO. You'd be having a nice quiet time and suddenly someone's radio would squack "hello big pooh bear, where are you?" or "Mom, Johnny's being a jerk!" It kind of annoyed us.
We also had connecting rooms and we brought something called Strap-its. We had them laying around leftover from an inventor fair project. They are elastic straps with velcro on the ends so they were easy to undo when you wanted to close your door. Got them at Gander Mountain. We kept the kids' door open permanently with some curling ribbon from a gift basket, and used the strap-its to keep our door open during the day. At night, we closed our door but left the dead bolt out so the kids could easily push the door open if they needed us. Bungee cords would work too and are probably cheaper. The doors are very heavy!
I concur about over-packing. We had way too much stuff!