I was able to find confirmation from a production designer, Andrew Probert (who helped design both the refit Enterprise from the films and the Enterprise-D), that the refit Enterprise was intended to have landing gear, although he himself is unsure whether it was the intent of the original Enterprise's designer, Matt Jefferies, that the triangles on the bottom of the first Enterprise were meant to be landing gear. In the box set of blueprints in Star Trek: The Next Generation USS Enterprise NCC-1701-D Blueprints there's a booklet with a roundtable interview featuring several production designers, and on p. 8 Probert says:
The Enterprise saucer was always designed to separate from the
Engineering section. I knew about this when I did Star Trek: The
Motion Picture. And if you look at the bottom of Kirk's Enterprise,
you'll notice two triangular items, which are two of the landing feet
for the saucer. Regardless of whether it was Matt Jeffries's [sic] original
intention or not, it's sort of the way that Trekdom or Star Trek lore
has labeled those features. So taking my cue from that for Star Trek:
The Motion Picture, I placed four landing legs in the bottom of the
Enterprise and created a very specific separation line on the dorsal.
There was also a set of officially-licensed blueprints for the first film, Star Trek: The Motion Picture Blueprints, which was based on the production designs of Andrew Probert and Lee Cole, and it labeled the landing pads as such (thumbnail images from the book can be seen on this page), so I think it can be considered pretty close to canonical that the refit Enterprise had landing pads.