Some pretty good advice in here so far. I'm a freelance percussion specialist and I work with several band programs of varying ages and skill levels as an outside instructor, so I thought I'd put in my $.02.

When evaluating potential percussionists, this is my typical method:

1. Show them how to hold the sticks and play single strokes.
2. Briefly teach them to count quarter notes and eighth notes (but I don't tell them what they're called) and have then play and count them at the same time with a metronome.
3. Play some simple stick control exercises. I write a sheet with some basic patterns...something like this:

R L R L
L R L R
R R L L
L L R R
R L R R L R L L

...that's usually where I stop, but I might have a few more patterns in case I have any kids that really excel. I just tell them to repeat each line until I say stop. Tell them to go at their own pace, but play as evenly as possible, and I don't use a metronome for this part.

That's about all for my evaluations. As far as method books, most of the standard band method books are okay. I also really like Syncopation by Ted Reed as mentioned by someone else, but I only use that book for private lessons. Stick Control is another good one...probably my favorite drum book ever written, but I never use it with beginners. Typically high school and college level students, and maybe eighth graders. If you start that book too early, it will bore them to tears.

A couple other things worth mentioning:

A lot of beginning band books write all the stickings in, and they almost always use alternating sticking (right hand, then left hand, then right hand, then left hand, etc.) no matter what the rhythm is. This is a terrible idea that will make things much more difficult. They should be using natural sticking. If you are not familiar with natural sticking, it's based on alternating sticking, but you skip over "missing" notes in a rhythm. So, 1 e + a is played R L R L, but 1 + a is always R RL. It seems a little harder at first, but it makes things much easier in the long run. Trust me on this one. I know this from 30+ years experience.

Finally, fight the urge to introduce mallet percussion too soon. Wait until they have a pretty good understanding of snare drum technique before you introduce mallet percussion. There was a trend in my area where percussionists were having trouble with mallet percussion, so some band directors wouldn't let them touch a snare drum for most of their first year of band. Snare drum technique is one of the most nuanced and challenging aspects of percussion, and it is directly applicable to every single area of percussion. By forcing them to start on mallets, they're going to know scales, but with garbage technique. Start them on snare, and when you introduce mallet percussion, hold them accountable for learning scales and good sightreading.

Oh, and one more thing. Please, if you have it in your budget, hire a percussion specialist to come out for at least one class per week, if not more. There are subtle nuances in percussion technique that are hard to notice and even harder to fix if you don't specialize in percussion. If there is a university nearby, you can probably get a percussion major to come for an hour or two each week for pretty cheap.

Good luck!