I'm in Providence and I forgot to bring the convenient spreadsheet I was using, but how does Vorel's position jive with the charger at 20n55e and GP at 40n55e? Also, wherever Vorel's goes, does he provoke an AoO because he becomes visible as he approaches 100ft of GP.
Anyway, GP's actions...he waits. The charger starts casting restoration defensively. [sblock] He cannot withstand another nasty breath weapon rider, and so he readies to greater dispel magic Vorel if Vorel starts casting. This will obviously affect Vorel but whether it affects the spell he's casting is another thing and is up to you. I don't think are any rules to govern it.
GP will still does this, regardless. [/sblock]
Your turn, Vorel.