First of all, my hat's off to your 60% savings rate! Wish I could do that well.
I'd focus on paying down the mortgage by the time you reach the 5-yr adjustment point. If I read your OP correctly, the rate might go up to as much as 5.5% at that point. Although your investments should be making more than that, that's getting a little high for my comfort level. Also, I'm wondering if you're going to feel the urge to upsize once your family starts growing. No telling what rates will be if/when you want to trade up, so having as much equity as possible in your current house will minimize the amount you have to finance on house #2. Yes, strictly by the numbers, it would make sense to max out the 401k before paying down the mortgage, because you'd make an immediate 15-25% from the tax savings, and you should be averaging a 7-10% annual return thereafter. But unless you can work out some sort of tax free 401k-to-Roth IRA ladder when you retire (and assuming that option still exists when your retire), you're going to have to pay a good chunk of that tax savings back eventually. And the average annual return is a guesstimate, not a guarantee. So, as another poster pointed out, the decision really comes down to whether you want the piece of mind that comes with having your house paid off.
Also, I'd look into how much it would cost you to get out of that car lease. I don't know the terms of your lease, but generally leases are a bad idea because you end up paying a large chunk of the purchase price and have no equity in the vehicle at the end.
But all of this is just fiddling around the edges. You clearly have your act together, and you seem to be on track to reach FI at a ridiculously young age.