Blupiper,
Presumably this will be an outdoor service. What you describe is quite apropos for the occasion. A dark commando sweater, etc is smart attire and more so for the piper.

I've worn it to many funeral gigs for no other reason than I was weary of the usual black argyll jacket.

I'm sure you'll make necessary preparations for cold weather piping.

My concern at those temperatures is keeping my hands warm & dexterous. For that, I've been using Wristies with the disposable heaters. Works beautifully. You should have time to receive a pair if you order quickly.

Slainte & Welcome,
steve