The other can of worms you would be opening is income tax. Your grandfather may be very generous but there are limits on how much money you can "gift" annually to family and friends. (link below)
So if all of you are in receipt of more than the allowances dictate, you might find find the can of worms you are opening isn't the one you think. I'd also point out the 7year rule - if your grandfather passes away within 7years of makeing these gift - the tax man could be over ther recipients like a rash
www.hmrc.gov.uk/inheritancetax/pass-money-property/exempt-gifts.htm
Wedding gifts/civil partnership ceremony gifts
Wedding or civil partnership ceremony gifts are exempt from Inheritance Tax, subject to certain limits:
?parents can each give cash or gifts worth £5,000
?grandparents and great grandparents can each give cash or gifts worth £2,500
?anyone else can give cash or gifts worth £1,000
You have to make the gift - or promise to make it - on or shortly before the date of the wedding or civil partnership ceremony. If the ceremony is called off and you still make the gift - or if you make the gift after the ceremony without having promised it first - this exemption won't apply.
Small gifts
You can make small gifts up to the value of £250 to as many individuals as you like in any one tax year. However, you can't give more than £250 and claim that the first £250 is a small gift. If you give an amount greater than £250 the exemption is lost altogether.
The seven-year rule - 'potentially exempt transfers'
Any gifts you make to individuals will be exempt from Inheritance Tax as long as you live for seven years after making the gift. These sorts of gifts are known as 'Potentially Exempt Transfers' (PETs).
However if you give an asset away at any time, but keep an interest in it - for example you give your house away but continue to live in it rent-free - this gift will not be a potentially exempt transfer. Follow the link below to find out more.
If you die within seven years and the total value of gifts you made is less than the Inheritance Tax threshold, then the value of the gifts is added to your estate and any tax due is paid out of the estate.
However, if you die within seven years of making a gift and the gift is valued at more than the Inheritance Tax threshold, Inheritance Tax will need to be paid on its value, either by the person receiving the gift or by the representatives of the estate.
If you die between three and seven years after making a gift, and the total value of gifts that you made is over the threshold, any Inheritance Tax due on the gift is reduced on a sliding scale. This is known as 'Taper Relief'.