Hi. Haven't done long haul flight with ds, but at 16 months we took him to Europe, and we took his favourite big book - "First Thousand Words", I think it was (Usborne). He amazed me with how still he sat for most of the flight, looking at the detailed pictures in the book. We also had a window seat and did much talking about the plane wings, clouds, etc. And had lots of food. Ds had quit breastfeeding by then, but I did take a flask of warm milk which I poured into a bottle for take-off and landing, to help with the ears/pressure. He was fine. I like pp's suggestions for new little trinkets to whip out periodically. Will remember that one!
As for parties, someone told me/I read somewhere (?) to have as many kids there as the child's age + 1. So that means inviting just one little pal! I admit we didn't stick to this rule for ds's first birthday last June, but we did have just two other little ones, plus close family who ds adores and feels happy around. It worked out fine.
This year, now ds has more little mates and we have more family over from overseas, we're splitting birthday celebrations into two manageable chunks: a close family afternoon on ds's birthday itself, and a joint party with another little boy on the weekend, with about five kids in all. Nothing too big or overwhelming.
I love the parents-go-out-for-a-meal thing! I'm going to ring the grandparents in the morning and book some babysitting for next Wednesday evening, I think. 
HTH