I have a video production company and have done a lot of transfers over the years. Those old reel to reel machines are a lot gentler on tapes than cassette decks when things go wrong. The tapes are more rubust too - thicker base. I wouldn't worry as much about brittleness either unless they've been stored in a bad environment. Extreme heat and spilling something on them would be a bigger concern.
I'd do it for you too as a favor but would also be concerned about loss in transit. If you have a deck, take some alcohol and swaps and clean the heads, capstan, and pinch roller. If it still runs you'll be fine.
