Your family, as the executors, can elect to pay inheritance tax, levied on houses and land, in instalments over 10 years. But if they sell the asset in that time ,then the whole tax remaining is payable on sale. It follows that it may be fairly easy to meet the demand, given that it appears that the value is not much above the threshold.
The executors can't normally get probate until the Revenue has been paid the inheritance tax, which in this case would be the first instalment.