Question about a will in Ontario I am married and I have a…

Question about a will in Ontario
I am married and I have a house in Ontario.
I want the house to be transferred to my kids after death. I agreed with the wife about this and she will not get anything from my legacy.
So, I will have a separation agreement stating the below conditions with my wife.
My question
1- Does it work to email the wife the separation agreement to her country (Russia) to sign and notarize her signature with two witnesses and she will mail it to me in Canada then I can sign and notarize or go to a commissioner to commission my signature with two witnesses. Is that a valid agreement and fulfill the condition that the wife will not take from the legacy?2- The will will mention that kids will get the legacy in certain percentage and will be witnessed and commissioned.
is that OK for the will to ensure that legacy will be to kids only.
3- What will happen if the witnesses die before me? is the separation agreement and the will still valid even if one or more of the witnesses are not alive?
is the stamp of the commissioner or notary is strong enough to make it valid after the death of the witnesses or I have to keep an eye to witnesses if one die I have to change the documents?
is it recommended to get witness from my friend or any one is OK?----------------------------------------------------------------------------------------------
ASSETS
12. The Parties acknowledge that they have agreed upon a division of all assets, owned or possessed by them as marital property or separate property. The Parties are in possession of all of those assets to which each is respectively entitled. Accordingly, neither makes any claim to any assets in the possession of the other.
DEBTS
13. The Parties agree that any indebtedness secured against, or attributable to, any item of property that either Party is receiving under this Agreement will be the sole responsibility of the Party receiving the particular property.
14. Neither Party will incur any further debt or liability on the other Party's credit. Any debt accumulated as of the date of this Agreement is the debt of the individual Party, regardless if the debt was incurred as a result of joint credit.
MATRIMONIAL PROPERTY RELEASE
15. The Parties covenant and agree that they are aware of the provisions of the Family Law Act of Ontario, and that it is their intention that the provisions of the Family Law Act will not apply to the status, ownership, interest and division of their property, either jointly or separately owned, nor to their future property, whether real or personal, and owned by either one or both of them, and the Parties further covenant and agree that it is their desire and intent by the terms of this Agreement to contract out of the provisions of the Family Law Act pursuant to Sections 21 and 54 of the said Act, and to make a full and final settlement of all matters of property, both real and personal, previously and presently owned by either of the Parties or to be acquired by either of the Parties in the future.
ESTATE AND TESTAMENTARY DISPOSITION
16. The Parties renounce all rights each might have in or to the administration of the other’s estate whether under any law of the Province of Ontario, or any Province or Territory of Canada, or any country in which any part of the estate of the other may be situated and further waive and release the other from any and all rights of every kind, nature, and description that each may acquire as a spouse or a surviving spouse in the property, assets, or estate of the other.