My niece travelled from Sweden to Hawaii at 8mo. She did fine.

I'd leave the baby with grandma and go enjoy Hawaii. But that's just me.

It depends on your kid. We are in Paris right now with our toddler and she did great with the time change. I think 8 months is probably early enough that she won't have problems adjusting, but some babies could be miserable. I'd still go though - I am of the kind that the more you travel with your kid the better off everyone is!

Took a baby that age to CA and he was up for the day by 2:30am every day of the trip--posters here are being surprisingly encouraging but i think at best it will be challenging.