They are capable of walking themselves. Or running as you mention. Kate mentions having to carry Madeleine home that evening so she wouldn't be keen to go around the long way.
So she says but David didn't say it at 6:30 when he said they were standing not panned out on the sofa.
1485 "But could you remember what Kate was wearing for example''
Reply "I can't, no.'
1485 "And did you actually set eyes on each individual child''
Reply "All three children I saw, yeah.'
1485 "And were they standing up' Sitting down''
Reply "Err they were generally standing up, yeah.'
1485 "Did they actually acknowledge you''
Reply "Err oh yeah, you know I'm very sure that if you'd have asked them, you know that evening or the next day they'd all say ah yeah, I popped in. You know I, you know I did know the children very well, we'd all you know, met up many times before err you know I, you know again I'd be playing with Madeleine you know in the, err the play area err you know during that week, you know lifting her up, twizzing her round and everything, I knew her that well, you know, to do that, and as I say err she'd definitely know who I was and certainly, as I say, just to reinforce that she looked very happy.'
http://www.mccannpjfiles.co.uk/PJ/DAVID-PAYNE-ROGATORY.htm