I would do
Jace for
Jason. I think it has a clear pronunciation and it's a more natural cut off than
Jay is.
I think Cassy from family would be pretty normal, but I can also see a boy getting gruff about it.
Lavinia-
Nia, Via,
Lia,
Laney,
Bonnie,
Vin,
Lin
I like
Annora "
Nora" or "
Nori" best.
~Anna~