I don't actually use my DSLRs for video much, but for my sins I'm a sound engineer. (Mostly conferencing nowadays, but formally bands, rock/folk/jazz etc. )
Yes you definitely want to use the -10dB pad, and the Zoom level might have to be a lot trimmed a lot lower than where you are used to having it. Not sure you'll get away with using the older mic straight into the camera if it doesn't have a pad...bands (especially in smaller local type venues) can produce some very high SPLs, despite not having the huge PA rigs you see flown in larger arenas/stadiums/concert halls, where they are set up to provide clarity rather than just sheer volume. If it's just for reference though....trim the input level down and you should get something vaguely listenable, not necessarily useable for the final edit though.
(think "phone" recording if you're really unlucky)
Also worth noting, smaller rooms and halls (sometimes due to weird architecture/decor) can have wildly differing types of sound depending where in the room you stand. If you can, visit somewhere beforehand and see a band play, to get a feel of the acoustics. Have a good walk around the room as they play, some areas (especially right next to walls) will sound really bass heavy, some areas really bass light. There are an awful lot of factors making up how it sounds (shape of room; wall coverings; amount of audience! -seriously-literally physical mass of lots of people makes a huge difference to acoustics!!!; audio tastes of engineer; quality of house PA system; etc. etc.) so I can't give you any hard and fast rules. But - try not to have your mic+Zoom right next to the back wall, or you'll want to make use of the bass roll off that that mic has.
What I really recommend though is......... try and get a good pair of isolating closed back headphones so you can hear what you've got going to disk. Personally I use/recommend a pair of Sennheiser HD25, they give you really good separation from the gig around you. Others are available - including full noise cancelling and ear defender style models, but HD25's are good because you're getting a nice reference headphone into the bargain.
Remember just because the LOUD bass lines/kick drum etc. are sounding awesome to your ears as you listen to the gig...that doesn't necessarily mean it will make a great video. Usually "live" music videos sound NOTHING like what you hear when you're there......they are a seperate mix, taken from the splits that feed the front of house and stage monitor desks.
Obviously that's not practicable for small gigs (and outside of an O.B. truck
) so instead, go and ask the engineer if you can get a desk recording.
Most engineers should have at least SOME way of recording a show.....be it straight to a CD rec deck, to a laptop, or with some of the digital desks now, straight to USB drive. Ask nicely.... let him know its for the video and remember to get his/her details so you can give them a credit, and they should be amenable one way or another. Even better, is carrying a second Zoom or similar, that you can give to them to plug straight into the desk output.
The only way he'll be an arse with you is if he's had a REALLY bad day cramming loads of load-in and sound-check into very little time....or if you come across as: "yeah yeah give me a damn recording you amateur" type of idiot.
Try not to turn up at the last minute, but also try not to pester him too much while he's still sound-checking. There's a "right moment" when the check's done and he's happy.
Using the two recordings....(your Zoom which is an ambient recording of the gig) and a recording of what was going through the FOH desk.... you should be able to mix them to more faithfully represent the band's sound, rather than just a mushy, bass heavy recording of what the room and PA have let you capture.
Hope this all makes sense!
p.s. for best results.....use an Outside Broadcast Truck!!!
just kidding. Have Fun.