The idea that if kids like the taste they may brush longer is a good one. However, Warheads children’s toothpaste has a pH of 3.2. This is very acidic, and could potentially demineralize enamel.
Even adults should not brush within 30 minutes of eating or drinking (water is okay), especially if we eat or drink something acidic (like that last glass of white wine?). When we ingest something, the bacteria in our mouths are active for around 15 minutes, eating and secreting acids. During that time, our enamel is softer, and we could brush some of it off. So, rinse with water after eating or drinking, and wait 30 minutes to brush!
Note that sugarless gum (with xylitol) will help reestablish the proper pH in your mouth. It is okay, and may actually help, to pop a piece in right after eating.