curry - i swear you're following me around this week 
You say you're a formal, robed choir - are you RSCM members?
if not, then it's really worth joining for their Voice for Life scheme.
WE have a junior choir (consisting of one, but we'll have another in september!) and they do a great scheme all laid out in stages for the kids to learn music theory and practice, as well as repertoire and all about being part of a choir.
We start them off at 7 or 8 (usually go by confident reader status) as probationers, they wear a cassock and do the Voice for Life White Level. When they've completed the white level (which should take about 3-4 months on average - certainly no fewer than 3 months), they get "admitted to the choir" and get a surplice. this is done in a proper ceremony in a church service.
when they've got white, they move onto Light Blue, at the end of which they get a light blue ribbon/medal, then they do Dark Blue and Red.
Junior choristers get paid for being part of the choir.
Ours is set up thus:
50p basic pay (which they get regardless of anything else)
25p per attendance (practices and services are counted as attendances)
we also have an attendance bonus - an extra 50p if they have 100% attendance in a month
dots are awarded for good stuff - effort, achievement etc (it's a small thing, so that every good thing can be rewarded, rather than having to build up to a good mark - in my experience, a chorister can quite easily lose a good mark before it's awarded because they've been naughty or not concentrating etc) - 5 dots = 1 Good Mark = 10p
so, at white level, a dot could be awarded for sitting nicely in a service, or for standing correctly, or for being able to read a phrase correctly (with rolling r and thuthing th)
our current Junior Chorister normally earns between £2.75 and £4.00 for a month
Weddings and other special services are paid separately from wages - we normally give 50p for Advent/Good Friday/9 Lessons and Carols, and Weddings are half the adults' pay (which comes out of the wedding fee)
We use fundraising events to raise money to pay the juniors - we used to have a subscription for the adults, where they paid a certain amount a term (understanding that it would be used for Choir Stuff like music and juniors)
We also have a buffet after the Advent Carol Service that raises money, and raffles every now and then. and we charge a set fee at weddings, so any spare after members have been paid goes into the Choir Fund. There are loads of ways to raise money (and often, parents will give £20 or so at christmas as a gift to the choir, which goes into the fund)