Updating post-procedure: I wish I had used a pad with wings for the day of the procedure and the next day. The silicone dilators have a semi-wide disk at the base and the lube and stuff oozed over the edges of even a wide liner. The square gauze pads provided at the surgery were thick and wide, but not plastic backed, so I still bled through to my panties.
Jeans were great at holding things securely in place! Dilating at home I am most comfortable wearing regular bikini panties with a pair of boyshorts over the top for an added tight layer or a pair of yoga pants.