It is expected that members of choirs are not all musically educated nor should that be made a requirement of membership. Thus, such responsibility is laid upon the one leading the choir.
Basic musical theory foundation needs to be built in each individual. Therefore, familiarity with basic scales is necessary.
I believe a few selection of hymns under C-Major (Not tranposed) would suffice such need (For example: Hymn 238: Till He Come-O Let the Words, http://www.christianstudy.com/data/hymns/midi/lifehymns/238.mid). And after basic mastery of intervals and harmonies, further introduction into other keys. follows.
[@more@]It is also important to note of the decision on teaching how to read just the non-staff scores is not quite enough.
I am currently learning basic music theory from a free web for chinese charistian at
http://c-highway.net/dong_list.php?pro_name1=%CB%CE%B4%F3%CA%E5%BD%CC%D2%F4%C0%D6&page1=1&userfiles1=thumb200508031123045269.jpg&id2=84
May be you should add this to your web.
But it is in mandarain speaking