I eventually paid for seats 52AB (US$39x2). Seats 51B and 51J were taken, otherwise I'd take 51AB or 51JK. We won't need to bother anyone to get out to go to washroom. Just hope the flushing sound from the washroom won't be too loud, and we can sleep through them.
https://www.seatguru.com/airlines/Tu...777-300_V3.php