Plenty of time. PEK has sterile international connections. Follow the signs for int'l connections, go through a cursory passport check (they will need to see the onward boarding pass which your wife and daughter can get from the connections desk if they don't have it yet). Once through the customs, down the stairs, through security and you're done. Very similar to HKG and very fast (even faster than HKG IMO as all * Alliance flights are close together and close to customs).