I'm going to disagree with the above. A disposable point-and-shoot with no controls (except the shutter) should not interfere with your tasks *AFTER* you've passed your checkout dives.
Don't take it on your checkout dives, but you may take it after you've been signed off.
Be aware that you should concentrate on diving first, and pushing buttons second. And that, only pushing a single button. (None of this what's my f/stop, speed, is my housing leaking, etc.)
I took a disposable point-and-shoot (only rated to 10 ft, but took it to 55) after my OW and took a couple of bad pictures. (Not to mention the camera getting x-rayed to death by the baggage machines). The camera stopped taking pictures below about 25 ft, but didn't leak. (Button mechanism stopped). I concentrated on diving, and took badly composed photos of my wife, a puffer fish, my instructor, etc. Do pay attention to your diving environment, though. If you're comfortable after your last checkout, I don't think a single-button point-and-shoot will overload you. If you're still feeling shaky with buoyancy, ascent, descent, etc., be careful not to let the camera prevent you from diving safely.
Good luck & have fun!