Dubai airport's lovely and the loos are very clean, so no problems changing etc. DD (23 months) and I have done about 8 long hauls already, so we're experts on a lot of airports and what to do and not to do
Clothes advice has already been given, so won't repeat. Take deodorant v.important !!
Take change of clothes for yourself, also very important (DD had a huge poo all over her and my clothes on the way to Vancouver once. Luckily I had a stopover in London, so was frantically running around looking for cheap clothes in designer T3!! Ended up with a union jack tshirt and £89 jeans from Reiss!!!)
Lots of Organix snacky stuff. Perfect for managing hungry tummies without overloading on sugar, plus they're not very heavy to carry. Take the number of nappies you need, then double up!
Take those big headphone thingys for the kids so you can stick on cartoons on the backseat TVs. All airlines now have universal headphone jacks so they should fit. The small earphones they provide are useless for kids, unless you spend the whole flight holding them to their ears (I did that once!)
Forget about watching any movies, and try and get a glass of wine, just enough to relax you, but not wipe you out.
Finally, cross your fingers tightly and hope they sleep all the way through! Good luck!!