Yes, you still need iTunes on a computer to sync to if you want to move music you didn't buy from iTunes onto an iDevice.
If this is your wife's first iDevice, I would recommend that you set her up with her own iTunes account. I would also suggest her iPad sync to HER computer (I'm assuming she has one). You can copy the MP3 files over to her machine using a thumb drive or some such and then sync them to her machine.
Personally (and this may be too late), I'd leave the new iPad pristine in the box until Xmas and then you and her have the discussion about whether you want to share an iTunes account or have separate ones, etc. and then let her set up the machine the way she wants it. I know there's a temptation to play with it and add apps, etc first but really I have found through experience that people really appreciate having such a personal gift pristine at first and going through the process themselves.