miles and vouchers - is this correct?

Hi guys,
newbie here. I don't fly often, but I ended up with a VA credit card and I'm trying to figure out how to spend some miles.
I have a wife, 1 infant and 1 child to bring with me.
I have 2 Premium Economy rewards and 1 Companion reward, all coming from the card.
If I book for me and the children in bucket L,R,B or Y, then I should be able to:
upgrade my seat to Premium Economy with 10k miles, and
use the vouchers to align everyone else to Premium Economy, right?
I don't know if it's actually worth it, vs. just paying the cheapest PE fare (it's going to be on either LHR - SFO or LHR - SYD, roundtrip), to be honest. Would be much more convenient to upgrade to Upper, but if I understand correctly, it would require at least 120k miles (60k for me and 60k for the child, plus some more for the infant), is that right?
newbie here. I don't fly often, but I ended up with a VA credit card and I'm trying to figure out how to spend some miles.
I have a wife, 1 infant and 1 child to bring with me.
I have 2 Premium Economy rewards and 1 Companion reward, all coming from the card.
If I book for me and the children in bucket L,R,B or Y, then I should be able to:
upgrade my seat to Premium Economy with 10k miles, and
use the vouchers to align everyone else to Premium Economy, right?
I don't know if it's actually worth it, vs. just paying the cheapest PE fare (it's going to be on either LHR - SFO or LHR - SYD, roundtrip), to be honest. Would be much more convenient to upgrade to Upper, but if I understand correctly, it would require at least 120k miles (60k for me and 60k for the child, plus some more for the infant), is that right?