I have simply picked up my TiW card on first entry to the park, on the first day of our first trip in a year. AFIAK, there is no advantage to ordering one in advance, and given that I typically don't get our APs until we arrive (all we have are vouchers, and I believe you need actual APs to get a TiW card) that's not possible anyway.
I think you meant that if you want to eat at your resort when you arrive, then you'll not be able to apply the TiW discount (because you won't have purchased the TiW card yet). Of course, if you're eating at a theme park, then you won't have a problem.