Here is a link that will tell you more about male calicos and the likelyhood of producing one. But basically the calico gene, when expressed in a male embryo, causes the death and reabsorption of the embryo. Something to do with males having XY and females having XX. (i think, i'm no expert!)http://www.messybeast.com/mosaicism.htm
I can tell you that your mamma may not produce ANY calicos, as genetics isn't putting two things together to get a third that is a mesh of the two (ie, that your white and orange male and white and black female will produce only white, orange and black kittens). It's a combination of genes in which some are dominant, some recessive, some only work in combination with XX others, etc. It's very complicated. You may be surprised and end up with all brown tabbies, or tuxedo kitties or something. Basically, as Gaye has mentioned in another thread, if you don't know the genetic history of the parents, and their parents, and THEIR parents . . . then it can be hard to tell what will happen.
That said, she may have calicos as I have NO idea what the genetic combination neccisary for calicos is! Thought most likely, if she does, they will all be female
As far as the effects of inbreeding, if they are siblings with the same mother and father, I would guess there is an increased risked of genetic defects, or kittens who are generally just not as healthy. Again, I don't know if that's like a 5% chance or a 50% chance.
Hopefully someone more knowledgeable and experienced with breeding and genetics can give you more concrete answers.
Best of luck with your future babies.