If I'm traveling with my long-time traveling partner, we will typically split the cooking duties (which includes meal planning).  About 2 months before we depart, we will share our selections so we can make adjustments so that we don't have too many similar meals.

If I'm traveling with almost anyone else, I usually make all the meal decisions and share a pre-trip menu with the participants.  This also generally means I do all the cooking.  (I guess I'm viewed as having some skill at it.)  Anyone has a veto on any meal choice (but they may be asked to suggest an alternative.)

dd