Okay then, the adults are 2 feet long with 3 hit dice so they could either be Tiny or Small.
I was going to go for Small, based on the feeling 3 HD is a bit high for Tiny, but I guess it's not that bad.
Hmm, there are a fair few references to their relationship with Black Dragons. A Wyrmling Blackie is Tiny and 4 Hit Dice, so I'll change my mind and go for Tiny.
Tiny Dragon
Hit Dice: 3d12
Pseudodragon: Str 6, Dex 15, Con 13, Int 10, Wis 12, Cha 10, +4 NA
Wyrmling Black Dragon: Str 11, Dex 10, Con 13, Int 8, Wis 11, Cha 8, +3 NA
Being Semi-Intelligent gives them Int 2-4. Their AC2 while flying matches a Pseudodragon's, but they have AC5 when not flying - I'd be inclined to interpret that as a flat-footed AC 3 less than normal, meaning Dex 16-17.
So, how about.
Minidragon: Str 8, Dex 17, Con 13, Int 4, Wis 12, Cha 5, +3 NA