Advice for event shoot

Hi forum,

I'm a fine art and stock photographer that doesn't typically do event, wedding, portraiture . I've been invited to a Chinese temple dedication and I thought I'd take some photo's to give to the head of the temple. I'm not being paid nor have I been asked to take photo's but I know they would be appreciated so I'd thought I shoot it.

I have a Canon 5D and various Canon glass. I was thinking I'd take my 17-40L, 24-105L and 70-200L. I also have a 430EX flash and a Rebel Xti I'll take a s back-up.

I imagine it will be coverage of the crowd, dragon dance, pictures of notables, etc. I realize to have really done this right it would mean meeting with the principals, checking the space out, etc. Bottom line is I'm not being paid and I don't want to set the expectation bar high on this one since I don't so this type of shooting for a living. I merely want to hand over a set of photo's better than the typical point n shoot stuff that will be taken.

Any overall advice? Any advice on flash photography? Aperture or shutter priority when using flash in this venue?

I'm a very experienced photographer but just not in this field and do not typical incorporate flash, I'd prefer pros comment here as I've already got the basics covered and know how to handle my gear.