I'd ask here. OP already has what the attire is requested and is wanting to deviate from that. A linen suit is not the same as a linen shirt. A linen shirt is more what you'd see at a beach. Polo is for the golf course and country club (though is quite common for business casual attire for corporate world).
In my mind I'd consider it on the same level as normal weddings but a consideration in the color palate to more suit a garden rather than a glitzy indoor wedding. The pastel is the clue. And the consideration towards the outdoor setting is the fabric of linen for the suit.
But when in doubt ask especially if you're going for the linen long sleeve or the polo.