If their channel becomes family vlogging, I think they’ll lose a lot of followers. A lot of people watch Shaun because they’re interested in rides and themeparks. He might be able to get away with it on his second channel, but if his main page becomes too baby focused he’ll lose a lot of his key audience.
He's already said that visits to midway attractions such as Sealife Centres, Cadbury World etc are moving to his second channel next year. That suggests he's going to turn that into the family channel while keeping the main one for theme parks.