Every other poster is correct; PL assumes you are bidding for only two people in a room.
That said, I have never had any problem with putting two adults and two children in a room on a PL bid. After winning, I always contact the hotel and request a room with two queen beds, and this request has always been honored. This has been in the US only.
One time we arrived at a Chicago area hotel I won on PL with our daughter. Our room had only one bed. The bell hop took one look and went up to the counter and changed our room to one with two beds.
It's just how much risk you are willing to take. I would think the majority of the time, if you are willing to be crowded and you could bring a pack-n-play for the baby to sleep in, you may find this works for you.