It is not the amount they are carrying but their size. Each ones counts as 2 medium creatures. So, between all of you and the giants, that's 15 medium sized creatures. You could do it if you have enough teleports.
In addition, I don't think the college will be happy about giants arriving, nor do I think the giants would be happy about going.
All that said, it could be done if that's how you want to go about doing it.
Well, I'll wait and see what the group would like to do, but I suggest we use the giants and teleport. I have enough teleports left to take two giants back without Nefario, teleport back, then take Nefario and one more giant back to the college. That leaves only one more for the rest of the group to deal with.
As far as the giants go, they'll be charmed for two weeks according to Enzo, so we shouldn't have to worry about them causing problems. Once back at the college, the wizards can go memorize more teleports and take the giants off campus after they unload the loot from the camp. We can then begin analyzing everything.
Hopefully Montaron can speak with the dead so we can question Bereth. Once all that is complete, I think we'll be in good shape. What does everyone else think of this plan?