If you give away cash, you won't have a liability to Capital Gains Tax and your daughter and granddaughter won't have to pay tax on it. You will have made gifts.
Normally, the value of gifts stay as part of your estate for seven years after you make them as you can read here unless they are covered by the exemptions which you can read about here.
I hope this helps but let me know if you have any further questions.
The gifts are relatively small. You should keep a record of them for your executor. However, if you are funding these payments comfortably from your monthly income and not dipping into savings then they can treated as "gifts out of income" which don't stay in your estate for seven years.
Your daughter and granddaughter won't have to declare the gifts but if they cannot be treated as gifts out of income, then your executor will need to include those made in the seven years before your death in the valuation of your estate.
Can you tell me how much you get from your husband's pension pre-tax please.
So, you are giving away about £16,800 out of a gross income of about £43,000. That is quite a large proportion but if you don't think it impinges on your lifestyle, then that's fine. You can use the £3,000 exemption and the £250 exemption if the gifts are not gifts out of income.