Fascinating thread! I don’t have anything practical to add regarding sewing the ties, but wanted to address your hesitancy to get involved lest you mess up, QuiltE.
If you decide to give it a go, it’s perfectly appropriate to tell your friend, listen, I’m willing to give it a try, I expect I’ll be successful, but honestly, I’ve never done this before and can’t promise I won’t mess it up. You decide, dear friend of mine, if you want to take that gamble.
She may say, heck they’re only ties, he’s not wearing them anymore, but let’s have fun with the process and if we get a great project at the end of this, that’s great.
Or she may say, these ties are my tangible memory of him, and I’d be crushed if they were ruined, so thank you, but I’ll find something else to do with them.
That honest conversation might help you both feel better.