Single here too, I'd put in one

Hey - good luck to you, this cycle looks great! Here's my thought - you already have a 4 year old, and it's looking like you are going to have some embies to freeze. I'd put ONE in. I know that if you get a BFN you will have to go back and spend $3-$4k to do FET, but that's a lot less than raising a baby. Heck, the extra medical care if things were to get complicated w/the pg of twins could cost that. Not to mention that priceless ingredient: TIME.

Best of luck in whatever you decide.