So I'm still distilling my audio setup with the Canon 5D Mk2 and the Zoom H4n Which has two balanced XLR mic ports. In 4Channel mode I can monitor all four channels - two from XLR ports - say two lav mics (two speakers) and then if I want plug in my RODE SVM (for ambient) into the back of the ZOOM to override the ZOOM's built in XY mics. I can adjust recording levels individually for the channels this way listening via over the ear headphones.

I've gotten two wired XLR lav mics that work great. I need two more XLR lavs and have considered this idea:

Buy a small 2 channel mixer like this Rolls MX34b:
Amazon.com: Rolls MX34b Live Mix 2-channel AV Mixer: Musical Instruments
The MX34b LiveMix - two channel microphone mixer. Although having many uses, this little mixer was originally designed with the video camera operator in mind. The MX34b is a two channel microphone mixer with balanced XLR inputs, phantom power, and stereo 1/8" (3.5mm) outputs. It has a stereo 1/8in (3.5mm) Auxiliary input for connection to any stereo line-level source such as an AM/FM tuner, CD player etc. And a 3.5mm headset mic in on the front for narration, etc.. Each channel has a Level and Pan control, and a separate headphone circuit allows for monitoring all signals without effecting the main output signal. Holes for a shoulder strap, easy-access controls, and smart Input/Output jack placement make the MX34b ideal for the live recording enthusiast. The 9 volt alkaline batteries ensure adequate signal strength as well as phantom power for your favorite condenser microphone.

Run the extra two lavs into it (it has Phantom power though it doesn't really say if it can do 48 or not.) then run the 1/8" out from the mixer into the ZOOM "stereo" port in the back. And finally from the ZOOM into the 5D mk2 mic via the attenuator i ordered last night. That way I could monitor everything through the phones initially then link the camera and the ZOOM. Of course once again I'm missing the real time monitoring but can at least hear a soundcheck of all 4 lavs before starting the recording.

Not to sound too Micorsoftish but I'd like to "leverage" what I own now and make the best use of this equipment.

Here's a link to the manual:
http://www.rolls.com/pdf/M_mx34b.pdf?PHPSESSID=4430e112718db2b53f1a4490685eaf10
It provides 18v phantom, which is usually enough for most XLR lavs, but there are plenty of mics you might want to use that do require full 48v.
The "headset mic" input is mentioned in the description and shown in the pictures in the manual, but I don't see it on the block diagram or in the actual instructions. You'd need to experiment with that jack to see what works.
There is a caution about not using mono plugs for in or out of the stereo jacks.
You would also need another attenuating cable to go between the mixer and the Zoom's back mini connector wouldn't you?

Thanks Jay,

The two lavs I have say they want 48 and the Zoom produces 48 so I wonder if this would work?
Also I didn't think about an attenuator between the mixer and the Zoom......hmmmm.....

Surely somone has figured this out for a basic workflow/process...I suppose with your help I can be the first.

I just saw a AudioTechnics ATR3350 omni lav (uses a watch battery for power so no need for phantom)with various connections including a mono 1/8". Now I'm thinking of trying to run two of these into a y splitter stereo male to two mono female 1/8" and plug that stereo into the back of the H4n and effectively be able to control recording levels on all 4 channels from 4 lavs. Two balanced XLRs and the two 1/8" connector lavs.

What you think?

I like AT mid and higher level gear, but their low-end mics are, as you would expect, pretty low-end...
I've never used that particular mic, but the specs have it with a very low sensitivity of -54db.
At that low cost you could try one, but I wouldn't get my hopes up, especially with the noise floor reputation that the rear connector of the H4n has.
Couple that with the finicky nature of watch-battery-powered cheap mics and I'd much rather invest in good XLR mics that can use a AA battery along with good quality adapter cables. Like the AT803 omni lav for example as a minimum.
Clearly it's more money, but it will be a much more reliable solution to use better mics that will continue to be good tools no matter what mixer or recorder you work with later.