Does the uncle's dream of his deceased mother bathing under abundant water, and his repeated hearing of the verse: "And whatever good you put forward for yourselves – you will find it with Allah. It is better and greater in reward. And seek forgiveness of Allah. Indeed, Allah is Forgiving and Merciful," indicate that it is good tidings and that her destination is Paradise, especially since she used to give much in charity?

The dream mentioned is a sign of good and glad tidings, and it is considered among the righteous dreams that a believer sees or that is seen for him, especially given what was mentioned about your mother's love for charity and her diligence in it. These are good signs through which you hope for good for her. However, bearing witness for a specific person that they are in Paradise or Hell is among the matters of the unseen, which are derived only from the Qur'an and Sunnah, and it is not permissible to exercise ijtihad (independent reasoning) concerning them. We hope for Paradise for the doer of good and rejoice in the signs of good, but Allah knows best about the ultimate outcomes.