The Greenbound template gives your summoned creatures the ability to cast spell-like abilities, at will, with the description:
Caster level equals greenbound creature's character level; save DC 10 + spell level + greenbound creature's Charisma modifier.
Now, Greenbound gives the +8 to Level adjustment. Some templates have no level adjustment. Others have a few here and there.
So, help a noobie out, what is the resultant "level" of your summons through Summon Nature's Ally, if only for knowing the caster level in this case?