option 5 6d Tamron 24-70, Tamron 70-200 f2.8
I'd say go for option 5. There's very little if any compromise on lens quality and you can always upgrade to 5DmarkX when your kids get older.
The only thing to keep in mind is that Third party lenses don't hold their value too well, so make sure you like the zooms a lot before you buy.
One other thing to consider about the Tamron lenses. While they are a great value for the money, and are optically superb, there are no lens profiles in the 5D3 or the 6D for them, nor are there ever likely to be. Profiles exist for most, if not all, current Canon lenses, at least the better ones. While it's not a deal breaker for me, it is part of why I ultimately decided on a Canon 24-70 2.8 II over the Tamron, even though I really liked the VC.