I've pretty much given up eating commercial pastries. I don't even ask any more.
Things are shifting very quickly now. My mother recently started paying attention to seed oils (I've been talking about it for a decade lol).
Palm oil has been demonised (incorrectly IMO), so I wouldn't use it.
Coconut oil is the safest bet.
You might want to consider preparing a leaflet explaining what fat you use. It will save your servers having to come find you & ask. A little sticker on the window saying "Free from seed oils" will 100% pull people like me in.
Vegans can be loud.
Seed oil disrespectors tend to quietly go somewhere else (usually to eat from home).