Shinkansen in Mid-Late April – it should still be okay to purchase tickets the day before or day-of, right?

Hello!

We will be travelling from Tokyo to Osaka during the week of April 19, and then Osaka to Nagoya later that week. Because this is still about 2 weeks from Golden Week, there shouldn't be much risk of Shinkansen filling up, right? I've only traveled to Japan during February and November, so this April time period will be new to me. I've always just purchased Shinkansen tickets the day before my desired trip, and it has not been a problem so far.

I think it will be okay, but if y'all don't mind confirming this as well, I would appreciate it! I've tried purchasing a ticket in advance through SmartEX a few times, but I've always had issues with my foreign credit card not being accepted.

Thanks!