Because there are unknown rarities involved then it's kind of more personal on how you feel about the worth of unknowns
The 2015 pets add up to a 2015 rare or two 2014 uncommons making you one 2014 uncommon short
The 2016s are unknown and most people see them as 'rares' due to the possibility that they could grow up with that rarity
So now it depends in how you see it...are they worth a 2016 rare each or only an uncommon or a common?
That will determine the true fairness of this trade
Personally, at most, I would put an unknown as an uncommon unless ive seen a lot of it around in which case i lower the rarity to common.
If you place all of the unknowns at uncommon then it makes up for the missing 2014 uncommon and makes the trade fair if not with a 2014 uncommon and animal egg as faint overpay
If you place the unknowns as common then it's unfair to you
Sorry if this was kinda confusing but hoped it helped c: