The waffle maker may be a problem; anything that heats up, rather than runs a motor (like the sewing machine) will be a heavy load, and likely the blow the transformer and ruin the waffle maker. Going back to my 1st experiences in the early 90s, I would say leave the waffle maker.
As for the sewing machine, just get a transformer....rewiring is basically a new motor, not worth the effort since a sewing machine runs quite well on a small transformer.