It might be a bit late, but I would also advise you to give a lot of attention to your 2 cats when you bring the new one home. I had to introduce cats a few times in recent years and, it might sound silly, but I found that talking to them helped. It is quite easy to become a bit overprotective of a new addition (especially if it is a kitten) and the other might feel a bit left out so by giving them some extra attention and a few treats helped me a great deal. The most difficult time was when my sister came to stay with me and took her 2 adult male cats with her, they bonded almost immediately with my female, it was harder with my 14 year old male but after a couple of days of hissing everything settled down, they might have not loved each other by they coexisted for almost 2 years. Shortly after their arrival I adopted a disabeld female kitten and the only reaction I had from my male was a sad look as if he wanted to say: Please not another one! There are the occasional squabbles but nothing I cannot handle.

Gook luck and please keep us informed.