You can make an estimate of what is a fair amount of alimony and child support depending on you and your children’s needs. Whatever you and your soon-to-be-ex-husband may agree on will be part of the final judgment. Whether it is fair or not will depend on your needs and expectations. But you really have to be careful and consult with a divorce lawyer before agreeing to any amount of support.
However, if you will let the court determine the amount, the computation for alimony varies depending on various factors the lifestyle during marriage, length of marriage, capacity of one spouse to earn and another to support, etc. While if the court will determine child support, then it will depend on a set formula based on the statewide uniform child support guideline (see http://www.childsup.ca.gov/Resources/CalculateChildSupport.aspx).
If you really want to make sure that you are getting a fair amount of support, work with an expert divorce and family law attorney for guidance.