DS, who is just six, has been handed down lots of Lego and playmobil knights and dragon toys. I think he is struggling a bit playing with them because, apart from mike the knight (which he has grown out of), and Robin Hood nothing he reads or watches has knights and/or dragons.
Going to get him the How to train your dragon books ( he would find the film too scary but is better with books) but everything else looks a bit too old and scary for a six year old.
Kingdom of wrenley Knight in training Usborne have a brilliant tales of knights type book plus lots of the usborne beginners - merlin, stories of king arthur etc Maybe knights handbook for factual stuff? Merlin & the dragons by jane yolen