Sounds lika a typical KISS setup!

Start with an AB Omni pair, 10 or so feet apart, at the edge of the stage (or hung if You forced to)..
If there's time left (or if you can do this at rehersals) put an ORTF-pair (or Blumlein 8's if your experienced), between the omins for an extra fill in the middle..
You'll have to listen to band to get an optimal position of both! Height is often dictated by how the musicisians are seated, but usualty 8 - 12 feet above stage level..

If the room is half decent, You probobly won't need any spots! Tho, sometimes something close on the piano (stereo pair) will be valuble in the mix if its contemporary music (gives you the posibility of a crisper sound). If you have channels left and you feel the need to use more mikes, put something on the drum kit, like a overhang and bassdrum spot!

The AB pair will probobly be enough when You get the position right! It's more or less down to what mikes You have!

/ptr

It HEAVILY depends on venue.

The oboe, clarinet and bassoon will all project forward quite well. The piano and trap set may be a challenge but the horn most certainly will be. If it's a church type setup, you're going to have a horn that overpowers in the mix in the lower mid range and disappears in the upper range.

If it's a concert hall situation, you're probably better off, but it still depends (how far back to the back wall? Shells? Acoustics??)

The way I would approach this in most settings would be -

Overhead pair (to pick up the balance of the ensemble - hopefully they can balance themselves just fine).

Spot mic on the horn (probably a Beyer M160 in front of and slightly above the horn player).

Spot mic or pair on the piano

SF12 or similar over the kit with top and bottom nulls avoiding the rest of the ensemble.

Then a wide AB flank pair to pick up the rest of the ambience.

Good luck and enjoy. Feel free to fill us in on what mics you have to choose from and what the acoustics and venue are like.

Cheers-
J