LT are really good for kids - there's usually a whole bunch of them running around saving the world, particularly at the Gathering - and each faction has it's fair share of younger members.

From age 5 the kids can participate in what's known as Kids Plot, regardless of which faction they belong to - run by LT staff, specifically for the kids, it helps teach them the rules and makes them feel a part of what's going on around them.

Older kids - probably from about age 10-12 - sometimes feel that they want to involve themselves in larger things, and will sometimes be seen in the guilds in small groups doing various jobs and making themselves useful where ever they can, which is great, and I assume often do the same in the factions (I tend to spend around 90% in the guilds myself, so couldn't say for definite).

I've only just seen your message on the L.T forums.
As stated by Anansii and Yal, kids are pretty well catered for and each faction will have their own fair share of kids running around, certainly at the Gathering. My group (the Order of Mithras) is in the Gryphons and even though the faction itself is quite a small faction we have about a dozen kids running around most times and about half of that number is from our group alone.
I started bringing my son to events when he was10 and at first I had the same concerns as yourself but after getting in the field and seeing everyone's reaction and how many other kids Jack could play with my concerns quickly disappeared. The one thing you can guarantee is your lad won't be bored.

As for your character type, playing a healer will keep you away from combat enough so that you pick up the rules easily enough. Plus there are never too many healers.

Anyhow I hope that helps mate.
As these forums are a bit difficult to access at the moment you may find it easier asking any larp related questions on the various facebook group pages.

Hope you enjoy the Gathering mate

Dave