Thank you for that clarification.
The intestate succession law is governed by statute 852.01
You are correct in that if there is a surviving spouse and children from a prior relationship, then the surviving spouse receives:
one-half of decedent's property other than the following property:
a. The decedent's interest in marital property.
b. The decedent's interest in property held equally and exclusively with the surviving spouse or surviving domestic partner as tenants in common.
The children would divide, equally, the decedent's one half of community property and 1/2 of their separate property.
As for an IRA in a community property state, while the decedent may still appoint a beneficiary of his/her choosing, the surviving spouse can make a claim on that portion which is deemed community property (ie earned during the marriage).
As for insurance proceeds, if the beneficiary was the estate, the company would have to issue the check to the estate; if there is a listed beneficiary, it passes outside of probate directly to the named beneficiary.