Since I live in NYC, I tend to avoid shows on weekends, since they cost more, they're crowded, and you can get better seats on days when people are less inclined to see a show. If they weren't sold out, they would still sell you one with a discount code (FHTMC1019) for $109, TKTS would be like $80ish, so you'd have some options. I would also say you both should enter the lottery on your way up for either or both shows for that day, cover your bases.
The matinee is down to less than 15 seats, so you're probably safe for that one selling out. But sometimes, they can be sticklers, and if there are four unsold seats, they will hold back on the SRO until someone buys them...