If I flower them now simply to determine sex, will they reveg outdoors or continue to flower?
Most likely reveg depending on where you live and the amount of sunlight outside, if you have already passed the summer equinox or live in a place where the days are 12 hours (12/12) then they will continue to flower however its still pretty early where i live
What are my chances of herms if they do reveg?
Not greatly increased, the stress from going to veg-flower-veg will vary depending on if you harden them off before you put them outside but i don't think it will be a major issue
Also will it be hard to determin sex with them being so small?
No because it will take time for them to actually flower and you will probably have multiple nodes at that time
Hope this helps brutha