James says he must take his camera so they can have photographs of all the stuff they do, and the things they see, and the places they visit.
Crackers is insisting that the weather will be gorgeous and they will be able to spend lots of time at the beach - so he wants to take their buckets and spades, so they can make sandcastles.
Oscar is going to take a map of Anglesey with him so that he can plan some walks for them all to do. There will be lots of interesting places to visit and Oscar will plot out routes so that they can travel through the prettiest countryside on their way.
They are also taking lots of things to do on their holiday in case the weather isn't very nice (though they are obviously hoping that there will be lots of sunshine and the opportunity to be out of doors as much as possible) - so they've got jigsaws, and puzzle books, and crayons and paints, and paper and pencils so that they can all write journals of what they have been up to every day.