Oh - one more absolutely vital thing.
CHANGE OF CLOTHING (and I mean complete one) for the nipper. Long haul maybe two changes. If you have some sort of an 'incident' and you don't have this, it's not a good situation.
Consider also a spare top for yourself, in case you should catch the brunt of, ahem, 'something'.
If for some reason you need a VERY large loo, the upstairs ones on the A380 (ie in J) are enormous. but tbh, for simple nappy changes, I actually find the confinement of a more regular sized loo makes it easier to stop him rolling away (and if you hit a spot of turbulence you can more easily brace yourself against a wall).
Also, when getting near to landing maybe be proactive in changing nappy etc before the usual rush once the '20 mins to seatbelt sign' announcement goes out. Although in F I think you're reasonably well catered for.