I think you should, specifically for the vendors working the entire wedding -- which can last 6 hours or more. Talk to your caterer about having meals prepared for the musicans/DJ, wedding planner and her staff, the photographer and videographer and their assistants. These are the vendors who will be working your entire wedding day and they will need food and drinks (non-alcoholic ones of course) in order to stay awake and energized.
The makeup artist and hairstylist, dresser, officiant, baker and florist (and their teams) won’t be spending more than a couple of hours with you so you don’t need to offer them a full meal.
As for what you serve it can be casual: sandwiches, wraps and salads. They won’t expect to be served the same meal as your guests. And for the cost, that will depend on your caterer. Some will throw it in and others may charge a $20pp fee. You can negotiate this with them or ask your wedding planner to coordinate sandwiches, drinks and a snack for vendors from outside source.