Intestacy, Deed of variation, trust fund abroad, help needed!!

Mathew

Hi all,
Hope someone can help!! Sadly I lost my Dad in last March, he died without a valid will. My Dad was re-married, however, only had two sons, me and my younger brother (same mum). His estate is valued at £330K inclusive of a house valued at 275K.
Grants of administration have been granted, with myself and his wife as executors. At the moment it is amicable in respect that we've agreed a three-way split in a deed of variation as followed
1. House to be placed in a trust, until her death and certain other 'trigger' events including re= marriage or co-habiting. The trust can be moved from property to property in the event she needed to 'down-size' with old age for example.
2. Remaining cash split 3 ways,
All was going well until we have hit a stumbling block in that the trust appears to only be valid in the UK. My Dad's wife is originally from Canada and potentially would want to go back. Does anybody know how to get around this? I have suggested bringing the trust to an end at this stage, however, she views that a third of the estate would not be sufficient to buy property outright in Canada and does not want to be restricted to the UK.
She has suggested reverting to the intestacy law as its set out and leaving a will to us. I am very reluctant to do this as this would potentially leave us with 20 years + of worry in that the will may have been changed or in any case, the will potentially could be challenged by others she may subsequently live with or children from a previous marriage.
Of note, my brother and I are both adults in are late twenties who were not financially dependant on our Dad on his death in relation to the Inheritance Act.
This is causing me a great deal of anxiety and am desperate to get the matter resolved ASAP! Any help would be greatly appreciated!!
Mathew