I agree.. if you can possibly make the phone call... that is the best way!!
I did what you did..and I ACTUALLY had people P.O that they didnt get a phone call!!! I thought a send out was a nice, fun way... but I was WRONG!!! If you can call some people that you know would prefer a more formal phone call then do that, and send something to the others??? Just my opinion... but I learned the hard way!!!
Good luck!