Khr2003

There is a designated parking area for each cruise terminal.  It's pretty simple once you get into Port Everglades.
You should plan on first going to the Cruise Terminal and dropping off all your luggage (and family) and then parking the car.

I, like @monctonguy am Canadian.  I live in Ontario.  I have many friends who make the 20+hr drive to Florida every year during March Break because the cost of airfare is too crazy for a family of 4 or 5.  I have no tips for you, as hubby would rather pay than drive, but know that you are not the only one out there, even if you aren't Canadian ?

A lot of information can be found here:
http://www.porteverglades.net/
Basically, upon entering, you'll see signs indicator where the ships are docked. Show ID and the boarding pass at the gate and follow the signs. You can drop off the luggage and your family in front of the terminal and then go park the car and making your way back. 
It's pretty easy and should be obvious where to go. 

Driven to Port Everglades several times, it is extremely easy and simple, don't stress.
There are signs on the highway directing you to the cruise port and the highway basically dead ends into the security gates at the port ... so you wont miss it :)
One important thing - they check passports / ids at the gate BEFORE letting you into the port, so make sure you have all your documents handy ... don't be the guy jumping out of the car, opening the trunk and digging through luggage while everyone else in line glares at you.
Once you are through security there is signage directing you to whichever terminal your ship is docked at. I would imagine Harmony uses the dedicated terminal for Oasis class ships, and there is a surface lot adjacent to the terminal. If you want covered parking instead there is a nearby parking garage that you should be directed to. The link provided above should give you a port map if you want to familiarize yourself ahead of time.