As i agree you should take in your Wife's plans for risk level into your over all plan (ie if she goes a 100% stock, and you go 70%, figuring equal numbers are invested, then your overall stock would be 85%.)
However, what you may also want to do is sorta mirror a target date fund, without paying the premium that comes with it. For example, im under 30, so most funds have me in almost all stock, and usually largely in one index fund. I looked at the index fund it was mostly invested in, and the cost ratio was like .08, or something near that, where the target date fund what around .8 if i recall. Might not sound like much, but over those first 10-12 years of my fund (I started in 2009) this would add up to quite an amount over the years.
Only difference on my part? When I hit 30 I may want to sale some of the index and move it to 10-20 percent into bonds. Takes me all of a few clicks (plus any time i spend deciding allocations) and i saved that much money.
I don't consider this that hands on, hell you could literally just look at the vanguard funds that your target fund has and pick them the exact same way yourself. The only thing that would prevent this is some of their accounts require 3-5k to open, so you may have to start with just one fund (probably a stock one) and after a year or so add on the others. Plus side with this plan also, is you eventually get into the "admiral" indexes, which have even a lower cost ratio.
I really like the sound of this approach. So instead of calling Vanguard and saying I'd like to roll into a Target Fund, I could have a preselected indexes for a fund?