Does Cadan like maps?
DS is so into maps just now, we have a map of a nature reserve place which he wants to look at every day and just talk about the route we took walking around etc. He also has a picture of a pirate map he loves to look at and wonder where the treasure is hidden. Then the other day I drew a map of our road for him with landmarks and he totally loved that and chatted and pointed for ages. The next day we began making our own map. Just 4 pieces of white A4 paper taped together at the back and brainstorming favourite places in our town, like the beach, park, Nana's house, it's a bit more 'free' this one and things do not need to be in the right place or to scale, he just scribbles colours and tells me 'that's the play park, that's the slide' etc and I write it on so I can remember what it all is when we look back at it. We just used felt pens as DS doesn't make mess with them - it's hard to get him interested in drawing long enough. For DS it gave purpose to drawing which motivated him because otherwise he doesn't really draw much.
Or maybe you could get some photo books out and talk about pics of days out and holidays?