I've took a look at your character creation guidelines for the campaign, they have quite a bit more in terms of stats than mine (we did 20 point buy). Also the equipment is pretty much standard in terms of starting gold. So your encounter suggestions might actually be a bit much for them. I can't tell you the stats right away since i don't have the sheets with me. I'll probably stick to the usual CR calculations and maybe increase the difficulty a bit ad hoc.
Probably some advanced templates and such. In case of the Vargouille, the armor for an advanced version is a bit much, AC 19 is really hard to hit for a 2nd level character (14+/65% misschance for a BAB 2 +3 STR character).
How would you balance AC? What hitchance should a character usually have?