Hi there, if you ds is starting half way through, they wont have any expectations of him so dont worry.
My d started in sept and was 5 months early, so far she has gone on from the ort no words books into books with long sentences(level 2, but most of class on L1 which is normal), my dd is only going onto more structured writing after Christmas and at minute they do rainbow wrting (teacher prints out big chunky 'Bubble style'letters and the children trace inside the letter using lots of diff coloured pencils, you could try this?
Also reading to him and helping him recognise certain words(action words, those you cant 'sound' out) like 'The' 'Who' etc, dd has lists of action words, some of which can be spelt, but are words that have a picture with them like 'You'-girl pointing her finger, 'this', pulling at your clothes...tbh, just basic recognition of words will be fine, the school will do all this.
Even at this stage its still about learning through play and without getting flamed here, dd's old nursery teacher told me its quite normal for Boys not to do things as quick as girls at the minute as theyre more intersted in running round and playing, so holding a pencil is something they will teach him when he's more ready.
He'll learn so much without realising
good luck
Oh and something ive found fab, are the 'Gold Star' books from toysrus or woolies, reading,writing, numbers etc, lots of activities to do in them and each page completed gets a gold star..dd and all my mindees love them