You might want to look at the reference book, "Smart Medicine for a Healthier Child" (I have a copy here - but I wouldn't blindly follow it - not all of the advice it gives is equally good). Your local health food store probably has a copy of it. There are things you can do besides L-Lysine (which also comes in a creme form).
The oral supplement of L-Lysine is only recommended for kids over 12, so you're right to beware of it.
You can limit foods with L-Arginine right before or during an outbreak
http://www.livestrong.com/article/27589 ... -arginine/You can give 100 MCG of Folic acid a day during an outbreak.
The book recommends giving a echinacea-goldenseal combination during an outbreak, but I would be very hesitant to give a child goldenseal.