Should I mention personal information in this thank you letter?
If I received a donor personally choosing to fund my education, I would include personal information in the thank you letter. The personal information I would include are things like "I grew up in .... I became interested in [scientific field] because..." and I would include it in the first paragraph. The reason that I feel that including personal information is appropriate is because you were personally chosen for this funding source (as opposed to applying to a scholarship committee, for example). Congrats!