Welcome Pennies, I am glad you have found us, but so sorry you are going through this.
Well, you have been through a lot very quickly, and it is no wonder you feel so rubbish, I bet not much has sunk in properly yet.
I think the best advice I can offer is holistic. Be very kind to yourself for a while and take each day as it comes. Try to have a laugh and enjoy life as much as possible, the treatment goes on for a long time, and you can't be constantly engaging your mind with it, you need to live as well.
You say you do not have much help near you, but do you have friends? I have found that i have had loads of offers of help, far more than I need, and not just from close friends but also from Mums at the school and all kinds of people. If they offer, accept that they mean it, and let them help. People really do want to, and I bet you'd do the same for them.
Others will be along soon with more advice relating to mastectomy, I have not been down that road and do not know much about it. MaryannSingleton will advise you to make use of the Breast cancer Care chat boards for real practical information - personally I have not done this as I prefer to live my life in denial but I believe they are very, very helpful.
As regards your kids - it is hard, I have a six year old dd. We have approached it by telling her that I had a lump which could make me poorly so i had it taken away, and then medicine to try to stop it coming back. She dealt with this OK. We also told the school so they knew and were ready to talk to her appropriately if she mentioned it to them (which she did). it was good to know her teachers were backing us up, and would let us know if they felt she was struggling with it.
keep talking to us, even if it is only to use swear words and for a shoulder to lean on.
Hugs to you and your family xx