I think we can find out in the Scripture exactly who these "little ones" are. There is several places that Jesus spoke about "little ones.'
Mat 10:5 These twelve Jesus sent forth, and commanded them, saying, Go not into the way of the Gentiles, and into any city of the Samaritans enter ye not:
Mat 10:42 And whosoever shall give to drink unto one of these little ones a cup of cold water only in the name of a disciple, verily I say unto you, he shall in no wise lose his reward.
Here we see that Jesus is sending out His disciples and referrs to them as "these little ones." You will note it is before they are converted, but they are in the process of learning the Truth.
Mat 18:1 At the same time came the disciples unto Jesus, saying, Who is the greatest in the kingdom of heaven?
Mat 18:2 And Jesus called a little child unto Him, and set him in the midst of them,
Mat 18:3 And said, Verily I say unto you, Except ye be converted, and become as little children, ye shall not enter into the kingdom of heaven.
Mat 18:6 But whoso shall offend one of these little ones which believe in me, it were better for him that a millstone were hanged about his neck, and that he were drowned in the depth of the sea.
Mat 18:10 See that you do not despise one of these little ones, for I tell you that their angels in Heaven continually look on the face of My Father in Heaven.
Mat 18:14 Even so it is not the will of your Father which is in heaven, that one of these little ones should perish.
Here Jesus says "Except ye be converted, and become as little children..." He goes on to say "do not despise one of these little ones..." and "not..one of these little ones should perish."
This is the same reference Mark 9 as above where Christ says... Mark 9:42 "And whosoever shall offend one of these little ones..."
Luke 17:1 Then said He unto the disciples, It is impossible but that offenses will come: but woe unto him, through whom they come!
Luke 17:2 It were better for him that a millstone were hanged about his neck, and he cast into the sea, than that he should offend one of these little ones.
Luke 17:3 Take heed to yourselves: If thy brother trespass against thee, rebuke him; and if he repent, forgive him.
In this passage in Luke Jesus is talking to the disciple, but in v. 3 He says, "if thy brother" meaning someone who is a brethren/believer, "if he repent, forgive him."
Every time that Jesus speaks of "little ones" He is referring directly to those that are disciples and followers, those He is teaching the Truth. Not those still in the church.
It is my opinion this is speaking of anyone that is coming into this Truth is a little one. So if they are seeking to know these Truths, then we should be careful, because that is the little ones.
mercy, peace and love
Kat