we went through this just a few weeks ago. i didnt want to take the risk of the crew telling us no and having one parent be stuck with our baby the entire 12 hour flight. that would have been horrible for both parents. our kid is 15 months and very active. even at 8months, i dont think your child will stay in the bassinet for the entire time. in the end we ended up buying 3 premium economy seats so that we can all be together. more importantly our kid had her own seat so she could lay down, eat, and play without us having to hold onto her the entire time. i believe the infant w/ own seat option was 70% of the full price.

also check out the Jetkid bed. we've cleared with Cathay ahead of time and they assigned our infant to the window seat where the kiddie bed could be set up. it's basically an extension so they have a flat bed to sleep on.

good luck. i feel your pain. gone are my days of travelling business undisturbed