Identifying a Child
Typically a child will be smaller than average. Some care is needed. Putting up a picture of a giant badger with the legend "If you are smaller than me, you can join the Sunday Club" is going to be potentially divisive. Especially for Old Mabel who is now just 4'9", and may end up in the "Sunbeams".
Just walking up and saying "are you a child?" is never a good tactic. It does have the advantage that you are being direct and straight to the point. But anybody who is not a child will be annoyed. Teenaged girls will be livid. And real children may inform you that they are, in fact, a stuntperson, or a train, or a supernova, or a lion.
Ideally, you should check passport photos or birth certificates. But be aware - children change quite quickly. They may not look much like their passport certificates.
Isolating Children from the Service
Under no circumstances must a child be exposed to a full-length, "adult" service. Remember the story of the Emperor's New Clothes. If your preacher is standing there in the altogether while claiming to be clad in the full armour of God, the chances of a child just pointing out the truth is very high. But more likely, if the preacher is claiming deep spiritual insight and a direct hotline to divine inspiration, having a small person shouting out "this is really boring" will be distracting. Especially if it causes other members of the congregation to join in.
No, church services are like radioactivity or paracetamol. Children need much smaller doses than adults. And the ecclesiastical equivalents of Calpol are many and varied. The old-fashioned approach is to have Sunday School. This is a direct descendant of the original Sunday Schools, except that instead of teaching basic literacy skills to all ages, we teach simplified theological skills to small people. Then there is the "Sunday Club". This is basically a Sunday School, but with the word "School" replaced with "Club". Or it can have some exciting name like "Scripturesplorers" or "SuperSundays" or ""Dazzlers" or something. Or it can be Messy Church, or - if your children are not naturally inclined to riot and insurrection under extreme provocation - Godly Play.
But the important thing is that you keep them out of the undiluted service. You can allow them back in for ten minutes at the end, or let them start off with you - but whatever you do, don't let them face the whole thing. Who knows where it will end?
Where it Will End
I'll tell you where it will end. It will end in chaos and recrimination. The whole point of keeping the kids out of the main service is to protect that valuable adult-space and me-time. The volunteers who bravely manage children's activities will do so for one or more of three reasons.
1) A spiritual calling and gifting to working with children
2) Nobody else would do it
3) They can't stand the main service either, but like going to Church.
Allow the children to take part in the main service, and other people's personal spiritual time will have to be sacrificed to those with shorter attention spans, or a lesser ability to fall asleep during the day. The claim that a Sunday Service is a time when God directly relates with God's people - something extremely exciting, in theory - is going to be tested to the limit. If it turns out that in fact church is just some old bloke going off on his favourite hobby horse - again - from the pulpit, padded out by some hymns in strange meters - then that's going to be pretty obvious. And a precious illusion is going to be dispelled by some shrill voice piping up with "Well, I can't see God. And now I need to have a poo!!!"
No, the ideal is that you keep the children out of the main service - just potentially serving up a "
Family" " All Age" " Fun" "Shorter Service" once a month to keep up the illusion that we are all, in fact, one body. The important thing to remember is that one day the child will stop being a child, and transition into being an adult. The transition has to be managed, and the classic method is as follows:
1) Send them to confirmation classes
2) Have them confirmed
3) Never see them again.
The trouble is, your small person may be transitioning into being a big person, but they are still going to be a young person - someone who has grown up with colour TV, tablets and smart phones. The Church has coped with transition, dealing with - and pioneering - new concepts in media, communication and playing with exciting new ideas, for most of 2000 years. Somehow, however, this all stopped in many circumstances about 1928. No obvious reason for it, just a sudden, seeping, cementation. Maybe it was a reaction to a flood of new ideas, or a response to a suddenly-changing world that decided the best bet was just to hold tight and hope it would go away. But the world just kept on changing, and something stopped.
Still, that won't matter, will it. The threat of the child has been identified, isolated, and transitioned into the outside world. Tthe ageless, ageing bubble has been protected from being burst by a sudden and unexpected incursion of youth. Things are still as they were, as they always were, as they always will be.