If you are visiting a place frequently (e.g., grandparent’s house), it’s well worth it for grandma/pa to get their own gear. My mom and in-laws, for example, have a high chair, a Pack ‘n Play, a monitor, and an umbrella stroller at their place; they even have car seats. Local mom’s groups often hold children’s resales, these are great places to get lightly used items for grandparents.
This isn’t totally necessary, but it will make your trips so much easier for years to come, especially if you have (or plan on having) multiple children. And especially if you visit them often.
If you’re going to a hotel or resort, many times these items can be provided upon request. I’ve only been to one hotel where they could not provide a travel crib (and it was only because they had run out).
Even the economy hotel and motel chains (Choice Hotels: Holiday Inn, Quality Inn, etc.) are generally good about supplying cribs and bedding. Many vacation rentals even have this stuff, but check the fine print before you go. You may also want to bring items that help your baby sleep, like a white noise machine.
If there isn’t a safe spot for your kiddo to sleep at your destination, you’ll probably want to bring along a travel crib or Pack ‘n Play (or another collapsible play yard). Will a regular PNP do the trick? Yes, absolutely. However, many parents prefer the lightweight-ness and portability of a travel crib. If you travel a fair amount, it’s definitely a worthwhile convenience purchase.