If you upgrade to F, I believe you get one or two checked bags for free/person (i'm 1K so don't know the bag benefit in BF).
Personally for me, if I'm flying transcon and I have a good Y seat (like exit aisle) I'd think twice but at $119, it's not that bad. I'd probably just roll the dice on a CPU or maybe use RPUs. If I had a lousy Y seat, hands down I'd do the extra $119. The other thing depending on how old your kids are, younger one's especially are not going to care if they're in BF or Y.
I did a trip from SFO to Belize last Dec and it was only $110 RT for upgrade to BF so I grabbed it even though total flight time was like 6-7 hours...