There are 3 rides in the WWoHP.
1) Harry Potter and the Forbidden Journey. It is pretty a next generation dark ride. It is located inside of Hogwarts Castle. You fly on "magical benches" throughout various scenes in Harry's world and encounter several dangerous creatures and objects such as huge spiders, the Whomping Willow(massive tree with an attitude problem that likes to take swings at people) and dementors(flying creatures that suck the souls out of people). This is ride has many scary elements and while it is not a coaster and does not go upside down, it does move quite a bit to simulate flying and you are at times flat on your back. The benches are on huge kuka robotic arms that move along a track, enabling the benches to swing freely. Your feet also dangle. There is 48 inch height requirement and there are over the shoulder body restraints.
2) Dragon Challange. This one is a full out coaster. Two to be more precise that move on separate tracks and duel each other(the ride used to be known as Dueling Dragons. This coaster does invert(upside down).
3) Flight of the Hippogriff. This is a family coaster. Small hills, short and somewhat fast. Very, very tame by coaster standards.
The rest of the WWoHP is comprised of stores, a tavern and a quick service restaruant. These shops are one the biggest draws for Potter fans and will probably not catch the fancy of anyone not familar with the Potter world. But they include Honeydukes Sweet Shop, Zonko's Joke Shop, Dervish and Bange's, the Owl Post and Ollivander's Wand shop. Ollivander's is basically a "show spot" where one person is chosen out of a group of 25 to have their "wand choose them". Ollivander's always has the longest lines of all the shops. There is also the Three Broomsticks for lunch and dinner, as well as the Hogshead Tavern for butterbeer, pumpkin juice and more adult beverages. FYI, no Coke products are sold inside this area of the park. As for characters, there are no Harry Potter characters in the WWoHP. However, there is the Frog Choir and the Triwizard Champion dancers who put on shows and then meet with fans for pictures. These two elements are straight out of Book 4 and movie 4 "The Goblet of Fire." Much of the Wizarding World might not make sense though to someone with no knowledge of the Potter universe though.
However throughout the rest of the park(and USF) there are characters out and about in certain place and certain times, such as the Simpsons, Madagascar, Cat in the Hat, Thing 1&2 ect.
As for Margaritaville, reservations are always nice to have. On your way into the park stop my the dining kiosk and make it. Easy to do and quick. And yes there are many shops at City Walk.
