That's a nice offer!! I play flute but don't know much about music theory. My flute teacher talked about it but my ears never picked up on what she was saying!!
What are some of the basics a beginner should know?
Here's some basics needed to begin songwriting (just the music part, I don't do lyrics).
1. know the Major Scale, the heart of western diatonic harmony.
2. understand how to spell the 12 Keys (sharps and flats in the keys)
3. understand the Intervals of the Major Scale, and how they sound.
4. learn to spell chord triads (harmony means stacked notes, like chords. Harmonize the 7 tones of the Major Scale, which will produce chord triads).
5. understand the Circle of 5ths and the V-I resolution.
6. understand the anchor notes of the Major Scale, and the other note's resolutions to them.
7. learn to harmonize the Major Scale into 7th chords.
8. learn the common tone relationship within the Major Scale harmonized chords.
9. Learn the minor scale (6th degree of Major Scale, called Natural Minor).
10. Learn how to write chord progressions (the I - IV - V and the ii - V - I progressions being the most used. Learn other popular progressions (will reveal how to play the chords to thousands of popular songs.)
11. Learn other Scales (Pentatonic and Blues), and chord prog. (8 bar and 12 bar Blues).
12. Learn chord notation (i.e., Cm7 = Cminor7 = C-7, etc. C/E = a C Major chord with an E note in the bass, called a 1st Inversion of a chord. Learn Roman numeral system for labeling chords, like large Roman numerals for Major chords, and lower cast Roman numerals for minor chords (I - ii - iii - IV - V - vi - vii).
13. Learn the Nashville number system. Useful for mapping out the composition of a song's chords. Also used at gigs to define a song to musicians for hire on the spot. You describe the chord progression using the Roman numeral system, then the style, and they got it (like a slow I-IV-V Country Blues in G Major).
14. Learn to read the notes on the Treble and Bass music clefs.
That's what I'd recommend for those interested in learning basic songwriting, and some skills in order to be able to play with other musicians.