The land lost is your friend here for models of Polaroid that may interest you. They also show compatabiloty with other instant films-some Polaroids have a mirror in the optical path, and cannot use certain modern films without reversing the image.
IMHO, the instax is the best gift camera, unless they may want to try another film in the future. Holga would allow for mf film, Diana's allow for...i have no idea, i think mf as well in the future.
The instax doesn't require peel apart or the risk of chemicals on hands and such.
Point, click, and print.