the general rule the younger they are the better, I did long haul with my then 3 month old son it was fairly easy, had use of the bassinette, for some reason he wanted to sleep alot not sure if it was the pressure, reamber to feed them milk on take of and landing for their ears, and if they keep crying the flight attentand told me to just let them as it is better for their ears, dont worry about anyone around you,
As for nappy changes if you get those small plastic sandwitch bags and put one nappy and wipes in each one it is easier and lready to go. the plastic change table is very hard in the toilets so take a small blanket or change mat.
as for any toys you spend half your time trying to find them or pick them up, so a plastic cup from the plane works just as well,
reamber to bring a change of clothes for yourself as well as the baby, when you are trying to eat food and drink goes everywhere when your trying to hold baby as well not much space,
we are flying long hurl in two weeks my babies are now three and one which is going to be alot harder, both on milk bottles, so I am trying to work out how I am going to do that, and daughter just learnt to walk so trying to get her to sit for 16 hours is going to be a nightmare.
I also found any thing that I could use disposable helped bibs, bottles etc
night flight is also good we did that when first baby was six months and very easy, only woke up on landing,
taking a stroller to the gate and also a baby sling is also a good idea, I think since your baby is still young it should not be to difficult,