Anna,
1. Go to the first frame where your son is in the scene. Using the selection tool, move the text identifier where you want it to be.
2. Turn on the auto-record button.
3. Step through the video and move the text identifier when necessary. Continue until the entire clip is done.
4. Play back the clip and check your work. Make changes as necessary
5. When satisfied, turn off the auto-record button.
Jim Kanter,
Digital Film Institute
http://www.dfilminst.com