Is it permissible to inform a well-off person to give charity on behalf of a deceased person whom I saw in a dream, and this dream was interpreted as charity, given that my financial situation does not allow for it?

The interpretation of a dream is conjectural, not definitive, and nothing is necessitated by this dream, for dreams do not obligate anything. Charity given on behalf of the deceased benefits them, and its reward reaches them by consensus. Your charity on behalf of this deceased person, even if small, is a good thing and beneficial to them. There is no harm in guiding others to give charity on behalf of the deceased, using the dream as an encouragement, whether you are able to give charity or unable, for this is an act of guiding to goodness.