You've gotten some great advice as usual. Just a couple more points.
On the kids, congrats on making the decision not to have any. You should not have them just because it is "expected" (at least it was by our parents). This was a decision that we made early on and have never regretted it. We love to see good parents with lots of good children, but it just wasn't for us.
As far as rental property goes, IMHO, it can be your best investment out there, but it does require some hard work (consider a management company if the numbers support it). But, by all means, read the books that were recommended and any others you can get your hands on. The more knowledge the better. We were able to retire at 36, mostly because of our real estate investments.
As far as the principal residence, you do get a great tax break for gains if you live their two years and actually have a gain (this benefit has been somewhat diminished by the cut in capital gains taxes). In my opinion, though, you should NEVER purchase more principal residence than you need to be comfortable. Use the extra money for investments such as rental real estate.
And lastely, avoid the nice car while you are young if you can, it's a terrible investment and just sits outside sucking up your money while you work and sleep. After almost going bankrupt with a sports car early in my career, I purchased a Toyota Camry and drove it for 12 years. I did regress, though, two years before I retired and drove a new corvette for a couple of years. That was a blast and set me back about $20,000.00
Good luck to you.