You will need to open an intestate administration case with the court in your jurisdiction. When someone passes away without a will, or trust, that person's property is inherited by the person's beneficiaries at law. This would include the surviving spouse and the children of the decedent. Unfortunately, the inheritance process when someone passes away intestate does not happen automatically. The inheritance must be confirmed and ordered by the court having jurisdiction (usually the trial level court in your county, unless there is a probate court that operates autonomously). I advise consulting with a probate attorney in your state.
If the surviving spouse wants to sell the property, she would have to probate the decedent's estate. In Texas, if the original will cannot be produced, it is presumed to be revoked by the testator and the estate would be probated without a will.
If the children were the biological children of both the decedent and the surviving spouse, then the administration should be pretty straight forward given the facts you recited. The decedent's community property would all go to the surviving spouse.
If the two children were biological children of the decedent but not the surviving spouse, then the two children would each have a 1/4 interest in the property and would have to assign their interest to the surviving spouse for her to be able to sell it.
If you would like to discuss this further, or would like assistance with this probate, please feel free to call.
David G. Voeller
If all potential heirs under the Texas law of intestate succession sign a deed to the peoperty to the suviving spouse she may be able to prepare an affidavit of heirship to satisfy a potential buyer on the chain of title.