I don't remember that quest but I don't think they are 1hd (1/4 CR) Kobolds? because I haven't seen any mobs with that low CR.
But even if they are, 5 CR 0.25 Kobolds and one CR 0.5 Hobgoblin =
Approximately 600 Exp for a full lvl 1-3 group.
Then 5 Kobolds and 2 Hobgoblins about 750 xp
Then 5 Kobolds and one CR 3 Ogre about 1400 XP
For a total of 2750 to a lvl 1-3 player (I would give slightly more to a Lvl 1 than a lvl 3 just because I'm a nice DM)
Or divided by six = 558 XP each for some pretty easy encounters.
But those kobolds probably have warrior levels added to them and are higher than CR 0.25?
D&D is not a solo game, but if a single player got ambushed by those mobs and killed them all I would give HIM at least 3000xp