I have had lots of problems with pink ivory. BUT, if I had to make pens from them (and I have had to), I would drill the hole with a little extra room. So, if it tries to shrink, it will not immediately "squeeze the brass tube" and crack.
Of course, the better you finish it, the less chance there is that humidity swings will affect it.
If you are able to make the kinds of laminations that Keith makes, you cut down the chances of cracking, since the wood is already cut in many places. (I can't do that - it's a TALENT problem)
You got the wood, you want to make a pen, go for it!! Several coats of whatever finish you choose.