Hehe, sounds like a load of fun... However I have some comments. Don't let them bother you, it's just my opinion not an edict!
Is the guild leader a child? I'm not sure how a child comes up with 20.000 tria and hands it to a governmental registry counter... I'd imagine there is an age limit for guild membership as well (if guilds are IC and not OOC... Which they should be in PS!).
Yes, Valiki is a child, the credits and such were all OOC necessities, as the guild system makes it easier to form a group like this. The idea behind it is to get people to use their imaginations a bit more, in their minds, this is a very important and top secret guild, or club. You remember what it was like when you a child surely? I for one remember starting groups like this among friends, it was great fun.
I don't agree with the existence of characters that are below 16 years (relative to human age, close to maturity) myself. Not sure what the settings team or PS team thinks about that. Despite this personal note though, I think it'd be more fitting to have a guild organized to entertain people (children), where the members are storytellers, entertainers, etc and not the people having fun. Else this seems more like a friend circle than a guild.
I, too, would be interested in hearing what the dev team have to say about child characters. I think there's a discussion in the wish list somewhere, I'll find it and link it later. An entertainment guild has already been done, and for some reason they never really last. And in anycase , much more fun can be had if you entertain yourself. These kids don't have to rely on others to have fun.
If it is a friend circle, I don't think you guys require the guild-tag... Mainly because other children might already be "guilded"!
But if you want the guild-tag, stick with the guild-tag. The topic post is very fun, so I won't mind much. 
Yes I have thought about other child chars that are for example in their parents guild, if they still want to join our club they may, it'll just be a little harder to give them ranks and to organise events and such. Still, I won't stop anyone from joining in our fun.
Sangwa, thanks for you input, I appreciate you took time to give me your thoughts. I can't say for sure whether or not this will work in the long run, but I'm certainly going to try. Let's just see where it goes, shall we?
EDIT: I couldn't find much on child characters, perhaps I should start a new thread, and ask for the devs ideas specifically. This is all I could find:
http://hydlaa.com/smf/index.php?topic=5668.0http://hydlaa.com/smf/index.php?topic=3184.0http://hydlaa.com/smf/index.php?topic=3790.0They're all terribly old though.
