Hello Bob,
I am a new father and my tip is that newborn's have uncanny timing when it comes to toilet habits....

So, keep a number of wipes on hand, nappy on when not shooting and be prepared for anything!!
I just tried to shoot a heap of shots with our three week old baby girl and we found it easier immediately after baby was fed and relaxed.
We also did what Derek suggested and found it useful. The other thing I did was quiz the resident hospital photographer for tips on what works and what doesn't.
Let us know how it goes.
Matt