As for the cable release, any standard one will do, but I have found that the better ones with a metal weave exterior are best. With cheaper ones I have had the exterior stretch out and the release no longer work properly. Here is an example:

What I ended up doing was having a short cable release attached to each lens I owned, it was a real time saver in the field not to have to change cable releases from one lens to the other.

As for the play in the lens board, I think the only issue there is if it is so loose that it moves while you are releasing the shutter . Here is an exercise to try to get an idea of how much of a difference it really makes. While looking under the dark cloth at your ground glass, move the lens board from side to side. You will see just how much it changes your perspective and also you should be able to see whether any light leaks in while you are doing this. If there is a light leak, or if the board moves to easily and messes with your composition, then use tape to hold it down or shims to remove the play, as advised above.

Have fun!