What is likely to happen with the house? If it's sold and you receive a share and reinvest that in another home in your sole name, then that would automatically count as part of your estate, and your executors would have discretion either to sell it or keep it, depending on what is best for your children in the unlikely event that you die before the youngest is 18. If it was kept, then it would be registered in the names of the trustees, on trust for your children, and at a predetermined time, perhaps the youngest's 21st birthday, then it would be sold and the proceeds divided between them.
Alternatively, the trustees may agree that the house should be sold straightaway and the money put into the trust.
If the house isn't sold but transferred over to you, the same applies, but if it's kept in joint names (unlikely), then it's particularly important that you do sever the joint tenancy to avoid your husband inheriting it as a joint tenant.
So far as guardianship is concerned, usually if the other parent survives, then they would expect to have the children living with them, certainly if they have parental responsibility and regular contact with the children. Sometimes, however, the other parent may have walked out when the children were tiny and would not be the obvious choice for them to live with. Either way, you can appoint a Guardian, but it's important that you understand that it's an expression of your wishes and not written in stone. If there was a dispute about who the children should live with, the court always has jurisdiction to make a ruling.
What you decide to put in the will depends on how imminently divorce proceedings are likely to be issued; if the likelihood is that you'll be divorced in 6 months, the wording will be different from if neither of you are in any hurry.
By the way, the life insurance normally falls outside your estate as the insurance company will normally act as trustees, but you can easily nominate your children instead of your husband.
I'm a will writer and happy to give any further advice if you want to PM me.