Hey, buddy-
I was exactly where you are a few months ago. Salt water has always been a dream of mine.. so I guess, in my case, I'm a mixture of you and your son put together... except I'm sure you have a bigger budget
PLEASE please hit me up if you need any advice. I have done just about everything wrong you can do and I've paid for it. Plus, depending on your personality and the types of questions you ask, some folks on here are SUPER cool and some are not.. I generally believe everyone's trying to help, but it might not seem so... so... anyhow..
Tips:
1) Get a skimmer.. the bigger, the better. I avoided getting one. Some folks will tell you that you don't need one, but, especially being a newbie.. it will help tremendously. You can even MAKE one (look on youtube) as a temporary trial and error thing just to see how it works. You're going to make mistakes stocking the tank and feeding too much and all that.. a skimmer will help keep your water crystal clean and it will truly remove SO much gunk. I have a 10 gallon tank as my training ground before I jump to a 40 or 55 gallon... and I have a 75 gallon-rated skimmer on mine.. Overkill? Maybe, but I'll tell you what, it keeps my water CRYSTAL clear, keeps odors at bay and pulls a LOT of gunk out. When I clean my glass of algae or stir up my rockwork and sand.. all of that floating gunk goes straight into the skimmer and out of my tank. Plus, I can keep it with me and keep using it until I cross over the 75 gallon threshold into big-boy territory. Trust me on this, dude.. get a skimmer.. all it is is a big device that will remove crap you don't want in the tank, keeps your water SUPER oxygenated and clear. It's worth it.. and then, when you move to corals.. you'll be set.
2.) DO NOT go with fine grain sand. My god, man- if I could give you any advice at all, it would be to NOT go with fine grain or 'sugar' sand. It looks amazing, it seems Caribbean and beach-y and fun, but it's an unbelievable pain. You'll learn more about water flow and pumps and all that in the future, but man.. this stuff blows around everywhere. It's like dust. You can't keep it off of your rocks.. or your corals.. and some fish won't pick up food that's fallen on it.. plus, it's impossible to vacuum. In every tank I have from here on out, I'm going with something bigger- maybe even gravel or crushed coral. I have this sugar sand right now and it STINKS. Can't wait to get rid of it. In fact, I may be consulting members soon to see how I can "swap out sand" to a bigger grain.
3.) Stock slowly. Seriously slowly. When you think you're being agonizingly slow, go slower. It will help SO much in the long run. Also, choose wisely. If you know your family wants clowns, well, heck.. go with clowns first.
4.) Become just as familiar with the Nitrogen Cycle as you are with the curves of a loved one. It will be your friend, but will also MURDER you if you don't respect it. I've had more crashes in my cycle and more swings than Lindsay Lohan leaving a night club. Add a fish.. let it get settled, add another a few weeks later. Now, you said your son wants Nemos. Clowns are about the only exception I can think of to this rule- if you want a pair. If you want a pair, and you want them to mate and swim around in anemones and corals and all that fun stuff, add two of the smallest ones you can find at the same time or pretty close to one another. The more juvenile, the better.. that way, your tank is the "only" home they'll really ever "know" and they'll do well since they haven't adjusted to anyone else's setup.. plus, the smaller they are, the less hard they are on the nitrogen cycle.
5.) Leave some swimming space in your aqua-scape.. but the more rock, the better. The rock is key. It is crucial. IT IS the filter.. it's also the home for your future friends like starfish and crabs and snails and stuff... fish in reefs don't need as much swimming space as you think.. caves and tunnels are awesome, but just use a ton of rock.. the lb per gallon rule is usually pretty good, but honestly, just get what you think looks neat and then add more. Like the old rule: when you think you've gathered enough firewood, gather more. It will never fail you.
6.) Buy stuff on craigslist and this club/forum. Local fish stores will ruin you. Sometimes you find a deal, and members here can tell you when/where to get the deals, but for the most part, just shop online if you have the patience and get your gear on here or craigslist... some of the guys on here have spent YEARS building GORGEOUS tanks out of scraps from craigslist. There are a ton of people here who can help you with that.
7.) keep your phone charged and handy when you're looking at buying a new fish or crab, or snail, or... and google it. Read reviews and check websites. It will save you a LOT of hassle from buying something that is beautiful but is really satan and eats everything and destroys your reef.. yes. This can happen.