Upvote:4
Their B-2 visas were stolen? Do you mean the passports were stolen? So they will get new passports and apply for new US visas, right? The purpose you have described in the question is perfectly valid for a C1 visa. That is, the purpose of entering the US is to transit, and no other reason to be in the US. So a C1 visa would work in this situation.
Getting the visa depends on if the interviewing consular officer thinks that the applicant qualifies for the visa at that point of time or not.
It is better to get the visas first and then book the cruise unless you are willing to forgo any cancellation charges in case they are unable to get the visa. You need to look at the timelines about getting the replacement passport and available appointments to make that decision.