Anything of value which is given to a minor has to be placed 'in trust'. For example, if someone leaves money or property to a minor in their will then, upon the death of the testator, their inheritance has to be placed 'in trust'.
Legally, until the minor reaches the age (usually 18) when the trust matures, it's the trustee who owns the money or property but with an obligation to pass it on to the beneficiary at the relevant time.
So you could create a trust for your granddaughter (with, say, her parents as the trustees of that trust) but it's easy for things to become extremely complicated.
Further, if you were hoping to give your granddaughter the property, but still keep receiving the rent until you die, it would be a 'gift with reservation', meaning that the value of the property would still be taken into account when assessing any liability for Inheritance Tax against your estate (or when working out whether you have to pay care home fees).
You'd also have to take very great care with the wording of the document which sought to transfer title in the property, as (unless you got it absolutely right), you'd normally end up with a situation whereby the trust you've created became the new landlord, with all rents being paid to the trust, rather than to you.