I totally agree that you should go for it - what an adventure!!
I assume they still think of your house as their home, so giving them set up money is actually wise, but I would not give them such a huge sum unless they have a specific plan. A month's rent plus key money, plus a month's food shop should be right. Keep the rest back for when they ask for it.
BUT,
- consider if you fit enough to take on a country cottage
- Sounds like you have done your homework, but paperwork and the actual work are quite stressful in themselves so do you have someone to talk things through with
- Make sure it is not just an escape you want, but a run towards that new life. (Is an alternative to get your grants sorted and sell it on with those in place)
Do you have friends/family or other support where you are going?
Plan well what you are taking, what will fit and what you will do with things like their bedroom contents.
Work out your budgets to ensure that you have enough for a quiet retreat when building work gets going.
A country cottage sounds idylic until you realise how far you are from services, doctors, hospitals, so discuss with local estate agents how saleable it will be after done, and for what price. It is unlikely to be your forever home if it is really rural, especially if you are no longer able to drive.
Do check how good delivery services are in your new area.
Take it at your pace and have fun with it