Max and Liz were in the car, on their way to Seattle where their pre-wedding party will start as soon as they arrive.
The two lovebirds didn't want to hold bachelor's and bachelorette's parties separately because they wanted all of their friends together, and Max and Liz didn't want to separate.
Since the kidnapping, Max, and Liz were sticking together most of the time; it was not about safety how much it was their need to spend every minute with each other because every moment counts. That ordeal reminded them that any moment could be their last and that they need to make the most of it, and they were happiest when they were together.
Considering how all guys abandoned Hunter's bachelor's party in order to join the ladies, no one objected to the idea of having one big, combined party. Besides, they did the same when Angela and Derek got married one month ago, and it was amazing.