When people refer to "tip night" they are usually referring to the last night of your cruise when you tip your wait staff. You will receive envelopes in your room that you can use to put the tips in. You can charge them to your account or use cash. You will tip any deliveries of room service in cash separately.
I imagine you can order pizza, but you can order almost anything else as well, cheeseburgers, chicken fingers, fries, soup, cookies, cheese platters etc. This is all included in the cost of the cruise. There are certain room service items that have a charge and some of those are movie theater type snacks, sodas, alcoholic beverages. You can order breakfast items as well as late night snacks. Like I said above tip each time.
ID you need a passport or birth certificate with a valid gov't issued ID. Just a requirement to reenter the U.S. when visiting foreign ports.
