updated 09/18/2013 AT 9:30 AM ET
•originally published 09/18/2013 AT 9:45 AM ET
“I can’t selfishly take journeys anymore because I have to take a little boy along with me,” she told reporters Tuesday at a Los Angeles press junket for the film, out Oct. 4.
Before taking on the role, the actress, 49, told producers she was in – if they made it “an amazing experience” for her son Louis, 3½.
“I said … make it so I’m not somewhere not paying attention because I’m so worried about ‘Where is he? Is he having fun? Is this a good life experience?’ ” she said.
In the end, it turns out, everyone on set went above and beyond for her little one.
“[Producer] David [Heyman] turned a backlot of a sound stage in rainy London into a wonderland for a 1½-year-old,” Bullock said. “Everything was bumper guarded! People go, ‘What is that?’ And I go, ‘That is to protect a child’s head! All of it!’ ”