I've just been through a very similar (although slightly more complicated) process with a redemption flight and was also reluctant to pay the seat selection fees. It's all good advice above and largely what we did. BA will try and seat you together anyway, and not deliberately split you up to make you pay for seats together. Also bear in mind that those with Bronze status will get seat selection 7 days out; there's not a lot you can do about that, but at 6 days out check what's available and there's a good chance (but no guarantees) they will stay available. Do your research in advance, and draw up a list with your husband of preferred seats, and some reserves in case you miss out. This is much less stressful than trying to figure out which of the available seats you want at OLCI, and then watching them get booked by someone else. Set yourself a reminder and make sure you can login to the BA app or website a few minutes in advance of T-24h and enjoy watching the countdown to check in opening!
I don't think any of the LAX flights are A380 operated, but if I've got that wrong and they are, bear in mind the upper deck CW is 3 across in the middle with the centre seat facing the opposite way to the two aisle seats. These are in line and OK to talk to your partner, but not quite as cosy for a couple as the 2 in the middle of the 4 across section on other aircraft.