People who have kids still want to boulder and sometimes they'll want/need to bring the kids along. Here are some suggestsions for child-friendly venues.
Peak District
Popular easy access areas with flat-ish safe areas include Cratcliffe/Robin Hoods Stride, Buckstone (Stanage) and Burbage South.
North Wales
South Wales
Lake District
The Buckstone has easy approach/access and flat surroundings making it suitable for kids.