non-resident Trustee of Life Interest Trust

I wish to assist my client (the widow) with appointing out of a NRB DT within two years of her husband’s death into a life interest trust in her favour and ultimately to their son. Both are potential beneficiaries of the NRBDT. They do not wish for the NRBDT to continue as it will be unduly complicated and the only asset is half the widow’s residence which is situated in the UK. The trustee appointed in the Will is a UK Trust Company who is agreeable to renouncing the executorship and trusteeship. My client is resident in the UK. However she wishes to appoint her son as the second trustee of the life interest trust and he is resident in New Zealand. Will this cause any problems given that on the widow’s death the half share in the property will pass outright to the son in any event under the newly created Life Interest Trust. Thanks for any pitfalls that I need to be aware of.