I just use W&N for placemats because I don't put hot pots on my placemats. I have used Insulbrite for hotpads & that would work great if you think the recipients will put something other than standard plate/glassware on the placemats.
Make sure to use 100% cotton fabric and thread then, as synthetic fibers can melt with heat. I would also make sure to quilt it no farther apart than 2" since this will be something that will likely be washed on a regular basis. Finally, I'd recommend washing them before you gift the placemats. Placemats are the one quilted item I make an exception for & use Clorox 2 along with detergent and for that reason, I pick lighter colors for my placemats.