I look forward to tapping your insights!
Back on topic: IMHO it really depends what classes and options are available. If you're mostly limited to Core rules, then the Sorcerer and Paladin are on the weak side, and +2 Charisma -- even if it's over and above what a Half Elf already gets* -- is probably not going to break anything.
If various other things are allowed, such as Snowflake Wardance or Blue Dragon Lineage or even Heritage feats in general, I'd re-consider. Basically, there are a lot of supplements that boost both Sorcerers and the value of Charisma. But if you don't allow those, then Charisma is weak.
Cheers, -- N