We're building that little church with intercessory prayer, evangelism, and teaching. Jesus said, "Feed My sheep." What do we feed them? Paul said Timothy was "nourished up in the words of faith and of good doctrine". And I said we need to teach our disciples both solid Biblical doctrine and solid Biblical faith!
"Can you recommend any good resources for a lesson guide?" Yes! It's called The Epistle of Paul the Apostle to the Ephesians. This wonderful book is only six chapters, but it's jam-packed with gold nuggets guaranteed to grow up believers. The first half or so deals mainly with what Christ has done for us and the remainder with how believers should treat one another. It's all good stuff, and there's enough material there to teach and train your congregation for over a year. Take it chapter by chapter, verse by verse, in some cases word by word! Don't dumb it down, but explain as plainly as possible deep theological concepts introduced here.
Another excellent course of study is outlined in Hebrews 6:1, what the author calls the principle doctrines, or foundation doctrines of the church. They are : Repentance from dead works; Faith toward God; Baptisms; Laying on of hands; the Resurrection of the dead; and Eternal judgement. These are the ABC's of Biblical Christianity, and you will do well to see your people are rooted and grounded in them.
With my home Bible Study, I took one session just to go over the books of the Bible, breaking it down by Old and New Testaments, the sections of each, and a brief summary of the contents and theme of each book. You'd be surprised how many believers can't find their way around the Bible! 'Tis sad!
Final note: please don't use the NIV; this version has so many passages left out, and many more translated in such a way as to leave the reader with just one possible interpretation or understanding. Give your flock complete Bibles, please! Love and peace always. Grow in grace.