I'm late getting to this thread but here's my .02 anyway:
Debeaking is not necessary for backyard flocks. Dewing, Dubbing, etc.-nope, not necessary.
The Mareks and Cocci vaccines are usually only recommended for large flocks. However, just using plain logic..do you really want to deal with an outbreak of either in your flock? The vaccines are very inexpensive. That said, I've gotten chicks vaccinated and un-vaccinated with no problems.
I had my last order vaccinated for Mareks only because all of my chicks get medicated feed, so the Cocci vaccine would be useless anyway. Lots of people stay away from medicated starter and lots of people swear by it. In my opinion, medicated starter (w/out added antibiotics) is a great thing. I've never dealt with Cocci and hope and pray I won't ever have to- I hear it's a real pain to beat.
I guess I look at it like this: I have my kids immunized for things they are likely never to come in contact with so I can feel they are safe 'just in case'- why not do it for the flock, too?
Good luck with your chicks and let us know what breeds you ordered!
On Edit: I don't know where you are located, but Ideal is in Texas and it's stinking HOT down here- make sure you get those babies from the post office as soon as they arrive and give them plenty of water!