Go ahead and get them counting in whatever system you would use with sixth grade. Use rhythm sticks or bucket drumming - you'll quickly see who should or shouldn't get a change to play percussion in the future. Do some breathing exercises and basic music theory. If you have a bunch of old brass mouthpieces laying around, play some buzzing games, again seeing who shows aptitude. Get soft Rico reeds in the 50 pack and cheap stock Cl or sax mouthpieces. Find your reed players. It may be harder to get flute head joints, but you can mimic the embouchure on a finger placed under the lip.

If you have or can get a class set of those Jupiter Testing kits, they could work really well.

Done right, this could be a gold mine for recruiting and instrument placement.

Friendly advice, if the first six weeks of your beginning band is boring, you might want to examine your approach. FUNdametals can be just that.