There is no need for you to share anything that you have inherited and it is absolutely none of your Mother's business either to know the amount you are to receive or to tell you what to do with it.
This sort of thing (interference, greed, entitlement etc.) is very common within families, but the Executors of the estate will tell you exactly what the law says you should do.
The Executors need to make it very clear to your mother that your inheritance is absolutely none of her business, nor is any decision you may make involving what you would do with it. She really does need to back off, she can leave your siblings whatever is left of her share in her own will if she's so determined they should have some of it, or she could give it to them now. What she wants is absolutely not your problem. She needs to be told that you could donate the whole lump sum to some obscure charity if that's what you really wanted to do.
IF you decide you would like to share yours, could I suggest you firstly clear any debts that you may have like mortgage, car payments etc. Then take an amount of that money for your own childrens' education, perhaps private school for now or funding for extra-curricular activities or tutoring followed by funding for each of them through University, it's easy enough to put money aside for it, that way you have no more foreseeable major financial provision in their lives until they are independent adults.
Then look at your own situation, do you want to move or revamp or extend your home? After you've deducted an amount to cover those costs, you could invest a lump sum where the interest would either cover your utility bills each year or pay for a nice holiday or give you a better pension when you need it, or pay for hobbies. Basically, it would be for your enjoyment, which after all is why it was left to you 
Once you've made your own family's financial situation more comfortable, you could look at anything that's left over and decide whether to share that with your siblings or not. I would suggest you first of all bank the money then take financial advice from several quarters and take your time in making up your mind how to have the best quality of life from the opportunities it will open up for you and your immediate family Whilst you are doing that, you can also see if your siblings decide to pressurise you pay for things for them. If they do, then you know money means more to them than you do. I'm sorry to raise that issue but I've seen an awful lot of family division caused by a false sense of entitlement from siblings and their pushy partners.
Above all, remember that the kind lady who left you that money would like you to enjoy her gift and remember her fondly for the opportunities you and your family can now enjoy thanks to her generosity.