Our school has 2 evening performances and no daytime ones and children under 5 are banned from both. This means that DP and I are having to go individually to the show on different nights because we have no family or friends round here who we can ask to babysit. I find this extremely annoying. Also, I think the lack of screaming infants, boisterous toddlers will ruin the atmosphere of the school play! I really don't understand why people think going to the school play is like some trip out to the opera that requires a silently reverent audience. Surely the real reason you're there is so that you're child can know you're there watching him/her?
The school have also sent home a letter asking who will be picking each child up on each night, but they've completely neglected to even give an estimation of the finish time. This doesn't matter so much since we have to go both nights, but it does mean that loads of parents who're going on the second night don't know when to turn up.
The same letter also bans photography and video cameras under the spurious cover of the data protection act. This is made all the more laughable by the fact that they are selling DVDs of the performance to make money. I think one of the secretaries just stuck something in about the data protection act (rather than, say, for child protection concerns, which would be entirely counteracted by selling DVDs of the performance anyway) to make it sound like an official reason. I'd much prefer that they stated the real reason, which is clearly that they want to raise some funds.
DS has to wear his dressing gown as a costume. They made him take it in last week and keep it in school, so he couldn't wear it at the weekend. That was slightly irksome too.
However, I do think the OP is BU about not changing the dates for illness. It's December, some of the children will inevitably always be ill. You just have to deal with it and wait for next year, I'm afraid.