4. Shower together. Lots of fun can be had in a shower or on a bathroom floor or counter for that matter. Use your imagination.
5. If you are cramped in a tent, camper or other tight quarters and sex really isn't a possibility, at least make the effort to express sexual interest. Hold hands, occasionally passionately kiss, sneak away on a walk, or share a look that says, "I want you, even if I can't have you right now." Expression of desire is better than blatant indifference.
Only you know what will work in your unique circumstances. I encourage you to be intentional, plan ahead and get creative with your sexual intimacy.
Family vacations aren't just about building memories, they are about building a strong foundation for your family. That familial foundation finds its greatest strength in a solid marriage. Spouses honor each other and their children (and I personally believe it honors God) most by treating their marriage as sacred. Sexual intimacy and expression of sexual interest is powerful, not just at home but on vacation too.