Setup
I just recently bought a new house for the same reason: expand for kids and ect. We don't have kids yet, but we want to be ready. Luckily my girlfriend agreed that I needed a bigger place to work on my cars. Our new place has a 30x30 shop with a lean-to on one side and another lean-to (both are full length) along the back which was converted to a wood working shop and is insulated.
I don't plan on getting a lift, but I'd like to add a lean-to to the other side so I can store two more projects I have. I'm in the country though, so a lot different than your situation. I've got the whole shibang for tools as well: engine hoist and stand, parts washer, sandblaster- the portable 110lb one, 4 roll away tool boxes loaded up, jacks and ect. so space is filling up quicker than I wanted, lol. One thing I love is the car dollies I just got. I currently am storing a 68 Tempest for my girlfriends dad so I have my jet boat in the main shop area and the dollies let me configure the Alpine around and then squeeze my Vette up along the boat so I have plenty of work space.
Like stated previously, the builder did not skimp on outlets when building it, and I love it. In my whole shop, including the lean-to's, I've got 26 outlets! Only 1 220 though... I don't have to fight to plug stuff in behind the cars and that's nice. I plan on doing a bathroom and definitely a sink and I'd like a washer for my coveralls at least. I do have a beer fridge as well
I've got some overhead storage that's kind of like a loft in a rear corner but I plan on moving it along the back wall. I guess what I'm getting at is my 2 cents worth which is +1 on getting a lot of outlets installed, overhead storage in the rafters or loft style, car dollies are amazing if you don't have them already, and don't sneak plumbing because we had to clear up a bunch of crap that was snuck in with a guest house behind my shop and it cost us a lot (thanks previous owner!). Also, I don't have good lighting in the main shop, so I'm converting to those new LED shop lights that look like fluorescents.
My dad got some and they are very bright. They only use half the power of standard fluorescents to, so they should help save some money on the power bill. Sounds like you'll have a pretty sweet setup though!
-Kyle