Cats, nematodes attack nearly every plant, even out there on your lawn and in the wild! This is how I understand it anyway, it is one reason it becomes so difficult to avoid the damage they cause in our gardens. Nematodes are everywhere, chewing on everything!
Except marigolds and a few other things, apparently . . . so, it may not make much difference where to put your marigold plants. However, heirloom tomatoes don't have resistance to nematodes usually, and not all the hybrids do either.
The
University of Missouri horticulturalists consider tomatoes, okra, beans, squash, peppers, carrots, cucumbers, muskmelon, eggplant, watermelon - very susceptible to nematodes. So, it looks like your idea of also putting them with the vining crops is a good one.
Steve