I do not see why it would not be safe to run a fused wire for the power seats without a relay, as long as the fuse is at the power source, not at the end point.
I'd run a separate 30 amp fused wire for each seat to be safe. Use copper 12-14 gauge wire.
You can find switched and unswitched 12v in the under hood fuse box by removing both covers. It's the metal strips at the rear of the box.

Here is a picture that shows the very outside terminal. There are 4 of them, the two to the center are hot all the time, the 2 outside ones are switched :