What's "crinkly" isn't the actual eyes - it's the skin around the eyes.
Note that crinkly here is evocative of "laughter lines" (it's a positive description). That's as opposed to near-synonymous wrinkly, which is evocative of deteriorating / saggy / lined skin from old age and/or constant bad-tempered scowling / frowning.
So with his crinkly blue1 eyes here equates to with a smile, with the additional implication that Dawes is a good-natured man who habitually smiles (so those lines are "engraved" in his face).
1 Also note the extremely positive associations of this particular eye colour, as reflected in the informal idiomatic British English usage blue-eyed boy - a boy or man who is liked very much and is treated well by someone, especially by someone in authority.