One 50lb bag each for your wife and yourself. None for lap child, but stroller can be checked at gate and doesn't count. Benefits are not additive - i.e. if you are Silver and also have MP card, you don't get two bags.

http://www.united.com/CMS/en-US/trav...edBaggage.aspx

I've never tried the above calculator before, but playing with it, it looks like reflects the written policy. Go to the tab "Any Flights".