There is sure to be an event somewhere near you - check out the Margaret Mahy nationwide read under Events everywhere. Most (but not all) are happening at 11am. If you live in Auckland, Cambridge, Tauranga, Taupo, Wellington Oamaru, Alexandra - and many places in-between - there will be readings, drawings and craft activities by local children's writers and illustrators.
I'm looking forward to reading at Brooklyn Library with Eirlys Hunter. We've both been raiding our bookshelves for our battered and much-read copies of some of Margaret's picture books - and Eirlys has even promised to lookout for a multi-coloured wig.