Rai, you can eat whatever you like. I find it causes me less anxiety if I avoid certain foods, but there's no actual reason you need to avoid anything.
It sounds right to me to start the pessaries on Saturday. They're not usually critical so early in the LP. It's common to start them as late as 3dpo. In fact, for IVF, my clinic doesn't give you any progesterone until you do your transfer, so you can start as late as 5dpo!