The Lighthouse Keeper books are great - My mum was a teacher and used to love them, now my kids do. They are available in 2 formats, one as normal picture story books (but longer stories than many, not too long, just a bit more so probably good for the ages you mention) or they have now been done as chapter book sized books. 2 stories in each, still colour pictures but bigger font so useful for them to maybe read to themselves as they get bigger.
Others we like include lots of the usborne lift the flap ones as mentioned.
My children love the 'poems for young children' book by Miles Kelly publishers, was cheapest on book depository last time I looked - under £7, over 300 poems, most classics, lovely illustrations, includes riddles as well.
just trying to think what else we have that would appeal to boys, we have 2 girls.
The Witches Dog books by Frank Rodgers are nice, they have colour pictures too but are early reader type chapter books (don't think they actually have chapters though as not particularly long), also Happy Mouseday by Dick King Smith (corgi pups), Dog on a Broomstick, Dogbird, erm Julia Donaldson's animal book, can't think what it is called but it combines the quick brown fox cub and the wrong kind of bark which are both great stories for children, colour illustrations and funny.
Have they got Paddington? They have now printed some of them as really lovely colour picture books so more appealing to young children than the original chapter books but I like the classic old versions too.
Enid Blyton's The Enchanted Wood, Magic Faraway Tree and Wishing Chair books are worth a look as well.
Alfie?
hope that helps a bit.