Hey there Bones!
I've got that same model calling my name down in my workshop. Got some aftermarket decals that are going to look sooooo sharp! Anyway, I personally don't like the thought of having to rescribe. To me it doesn't matter if the kit has raised or recessed panel lines. Even the recessed lines, I feel, seem out of scale even on Tamiya kits. But that's another topic for another time.
Getting back to the topic, I've had some kits with raised lines which got erased after filling and sanding was all done. I would take my scriber and scribe the part of the line which had been sanded away. In my honest opinion, after the model has been painted, weathered and decalled (or is it with one "L"?), you really cannot see where the raised line ends and your scribe work begins. I try to limit how many panel lines are obliterated by using masking tape to protect the areas which do not need sanding. That leaves just a minimal amount of lines which need touch up.
It sounds like you want to do a real bang-up job on this kit (and who wouldn't?) so I thought that maybe this technique might be of help in the interest of time. I've always wanted to try to rescribe lines to see how it works for me. I hope your work turns out great! And don't forget, this is going to your father-in-law so you know he's going to love anything you do for and give to him.
Eric