One moving-coil mic for two flutes will be.... challenging, to say the least. Something with a wider pickup pattern, like a Sennheiser 421, might work, but I can't imagine it being preferable to using two mics. An SM58 on each flautist would work fine.
A good multipattern condenser would open your options up tremendously. AKG C414, Austrian OC818, Neumann TLM107, something like that. A single of any of those would be useable on two flutes for sure.
As someone that plays classical flute for wedding ceremonies, using one mic for two flutes is not ideal.
My trio (F,Vi,C) has done many outdoor "concert-in-the-park" performances that require sound re-enforcement..
My favorite mic to use is my Senn 421. It seems to draw-out the low register of my flute really well.
The 421 is rather big & in the way, so I usually just go with a Senn 835 (with windscreen) and call it a day.
What I have found to be the best position for a mic (on a flute) is 6-10" in front of the lip plate.
Adding a windscreen will cut down on the bit of air that passes over the air-reed.
If I were to attempt to cover two individual flutes with one mic I would use one of my choral mics: Shure MX202B/C
Getting back to weddings: playing flute "acoustic" works for me .....