Doing the school round is well worth it in its own right - I've done it without anyone going to the megafinal some years. For those who qualify, you can give them the information for their parents to decide whether or not to take them. I usually put my contact details on that information, so that they can get in touch with me if they want to ask me about it, or want to share transport. I also run the names past the head, as I am just a parent, in case there are any "pupil premium" children - I would hope that in that case they would offer to pay the entry fee.