There is no way to really tell in advance, but using some averages I would think 16 mature eggs would be a conservative target goal to keep in mind for a shared cycle IMHO. When they are tracking follicles it is hard to know how many will have mature eggs.
If the average fertilization rate is 75%, that means 12 of the 16 mature eggs fertilize.
Then if on average 40% of those 12 fertilized eggs become blastocysts, there would be roughly 5 blastocysts total from the cycle, enough for two people.
Every cycle is different though, there are way too many factors to tell what is going to happen or if you will fall within the averages or surpass them.