IHT and making a will

Hi
Myself and my partner own a property in Extremadura we are fiscal resident but we are about to return to the UK to live.The property was bought for 160k in 2007 with no mortgage.I don't know what it would be valued at now but considerably less as not only have prices plummeted but for the last 2 years there has been an on going problem with access,which still hasn't been resolved.
It is owned 50/50 between my self and my partner (we are not married) we have 2 children 18 and 16.I want to make a Spanish will before I go back to the Uk and want to know the following.
For tax purposes is it better to leave my 50% to my partner and 2 children and him the same or just to leave it to the children for tax purposes
Thanks
Jayne