do you want video?
then the D5000, or, If you're willing to spend more(much) then you have the D300s.
otherwise, the D90's a great little camera, and the successor to the D80, which was great as well! never owned either, but used all 4. all great cameras. the D90 and D300s are by far the best in terms of "ruggedness" if you ask me.
grab a 50mm 1.8D, or if you're a little more spendy, the 1.4G(no aperture ring). that paired with the kit 18-55VR lens makes a nice little combo, especially for the wife. That's what I'd tell my mum to buy if she was in your shoes. Since I'm not married, I used my mum as a ref. . I'm 21....
take here with you, touch em', grope em'(sorry, had to ), find out which one suits BOTH of you the best, or whoever the primary user will be...
-Dan