You mentioned you are going for 5 days and have park hopper - so yes, you can go to all 4 of the theme parks (Magic Kingdom, EPCOT, Hollywood Studios, and Animal Kingdom)
Are you staying on property at one of the Disney World resorts? If YES make sure you take advantage of the Extra Magic Hours (a certain park will open a few hours early or stay a few hours late most days for resort guests)
Do you have the Dining Plan? If you don't (and are staying on property) get it. It will cost you WAY less in the long run vs. paying out of pocket for meals.
Here are my list of do-not-miss attractions for each park:
MK:
Big Thunder Mountain
Splash Mountain
Space Mountain
Pirates of the Caribbean
Jungle Cruise
Haunted Mansion
Peter Pan's Flight
Buzz Lightyear's Space Ranger Spin
Monster's Inc. Laugh Floor
Tomorrowland Travel Authority (this is an awesome chill out ride, never a wait you just hop on and it gives you a relaxing tour and some cool views then you hop off, a great way to take a break from walking)
Snow Whites Scary Adventures (kind of sucks but its being closed down on May 31 forever so this'll be your last chance to ride it - it's being replaced with Seven Dwarf's Mine Coaster)
(Things to AVOID - Swiss Family Treehouse and Tom Sawyer Island... trust me)
EPCOT:
Mission Space
Test Track
Soarin
Turtle Talk w/ Crush (your kid will love it)
The Sum of All Thrills (Located inside of Innoventions EAST - this is an awesome design your own coaster then ride it on a robotic arm simulator that is often overlooked)
Club Cool (This is not a ride, it's a FREE soda sampling shop, lets you taste different sodas from all over the world and it's amazingly awesome! It's kind of on the side of Innoventions WEST, or just ask a Cast Member)
Space Ship Earth (aka the giant golf ball)
World Showcase is awesome and I love walking through the different countries and just taking my time and paying attention to detail. This is also where you will get the BEST food in all of the parks, so choose wisely
Every country has it's own food and its all amazing. Also booze. There are two rides here, one in Norway and one in Mexico, they are both chill out sit on a boat type of rides and are a good break from walking around the world, but neither are worth a long wait.
Hollywood Studios:
Rock n Roller Coaster
Tower of Terror
Toy Story Midway Mania (SERIOUSLY GET HERE WHEN THE PARK OPENS AND BASICALLY RUN TO THIS RIDE OTHERWISE YOU WILL HAVE A 75+ MINUTE WAIT AND FAST PASSES WILL BE SOLD OUT)
Star Tours - this was recently upgraded to better motion simulation, 3D film, and a randomized course (beginning middle end are randomized for a different ride every time)
There's also a LOT of shows, and a lot of them are really cool so enjoy them at your leisure. I'm partial to Indiana Jones Stunt Show, Lights Motor Action, and Backlot Tour (which includes a water/explosion show and is not just a boring tour I promise it's really awesome)
Animal Kingdom:
Kilimanjaro Safari is awesome - go earlier for more active animals
Kali River Rapids (possible to get soaked or be bone dry, ride last just in case you dont want to walk around dripping wet all day)
Dinosaur (can be VERY loud but is otherwise awesome and shouldn't be missed)
Expedition Everest of course
AVOID - Rafiki's Planet Watch (super boring, nothing to do, only way in or out is a train ride and you're kind of stuck there until the next train)
Now for my FOOD RECOMMENDATIONS assuming you have the dining plan.
Almost any park: TURKEY LEG (so good and ungodly huge)
Polynesian Resort (on MK monorail): Ohana's Dinner Buffet - omg soooo good, come starving.
Polynesian Resort: Kona Cafe - awesome for lunch or dinner, also great sushi at their sushi bar
Magic Kingdom: Dole Whip - this is amazing pineapple soft serve you can't get anywhere else in the world
Contemporary Resort (on MK monorail): California Grill - Come here for a nice, fancy dinner with amazing views assuming your kids old enough to go out for a fancy dinner. Semi formal dress suggested.
Epcot Morocco: Tangerine Cafe - Schwarma Platter
Epcot Italy: Via Napoli - Seriously only worth it on the dining plan otherwise its like crazy expensive but this pizza is sooooo good. They import the water and flour from italy just to make the dough
Epcot Canada: Le Celier - The BEST steaks you'll ever have
Epcot The Seas: Coral Reef - Entire wall is an aquarium and they serve awesome seafood.
Animal Kingdom: Yak & Yeti - Amazing asian food, and you MUST try the mango pie (from the restaurant not from the take away stand next door)
Hollywood Studios: Sci Fi Dine In Theatre.
Other general tips: Parades can take a long time (from waiting for them with a good spot, to finish, plus the huge rush of crowd afterward) I definitely recommend watching a couple but do not try to catch every parade. It's a great time to enjoy decreased wait times on other rides.
Fireworks show at Magic Kingdom is awesome, so is the "pre show" where they do some really awesome projections on the castle.Get a good spot and enjoy at least once. I recommend the balcony area of the tomorrowland terrace. Another good spot is the MAIN STREET train station. Directly in front of the castle at the opening gates, and you can be up on a platform above the rest of the crowd.
If you can, rent a car it's much better to get around on property with your own vehicle rather than need to rely on the bus's schedule (eats up time waiting for the bus, and the other stops etc) especially if you are trying to meet any kind of reservations.
Make sure you utilize your fast pass, you can get one for each ticket once per hour OR after you've used your open fast pass whichever comes first So, for example if you get one at noon, and use it at 12:30 you can grab another one with no wait. Or if you grab one at noon but you can't use it until 6pm, you can get another one at 1PM.
If you have any specific questions, I'll try to answer them for you. Have a great trip!