Running a dehumidifier to keep the humidity down will work.
If you can get under the toe-kick and or up against the far
wall with a saw, you can cut a kerf anywhere to allow for
expansion, but if you want the cut concealed, you'll have
to move whatever is going to be covering the cut.

I started a dehumidifier in the basement area below/behind the kitchen
in mid-August, with no apparent change. I suspect I need to set the
humidity lower or run it upstairs in the room itself.

You are exactly right - I am very reluctant to try to move the cabinets
(fancy, cherry-veneer, granite tops, on both sides of room). I have
called several flooring places to come give me their opinions.

Regards,
Teo