It stands for Congregation of Mary Immaculate Queen.
I'm surprised you've never heard of them, they are the second largest traditionalist group in the world. You can read their positions on their website CMRI.org
They hold the sedevacantist position but do not require it for mass attendance or to receive the sacraments. They won't question you about it. One of the best things is that they are extremely accommodating in regards to sick calls, baptisms, and other needs for people who are in difficult situations such as living far from mass.
The particular chapel I recommended, Our Mother of Perpetual Help, has Father Gabriel Lavery as its current priest. He is a very kind and pious priest, and if you want to call him and ask him questions, he will gladly talk to you. I have attended mass at this chapel many times over the years and find it to be a good situation for managing small children and I find the people very friendly, which is nice for a traveler. (I'm in a similar boat, if you haven't guessed, lots of young children and difficulty getting to mass)
I've been to 7-8 CMRI chapels from coast to coast and I have never heard a liberal sermon out of any of their priests.