Basically, what the others have said but I'll add - as relative beginners you should be playing music you are really familiar with. I.e. if you just find simple "lead sheets" (chords and lyrics) for songs you listen to and could sing in your sleep then learning to play them will be much easier because you'll know when the rhythm doesn't sound right, etc.
Second, sing (even if only softly to yourselves) the song as you play - again, if you know the song and you can't sing it then you'll know something isn't right with the rhythm.
On youtube there is a whole series of bass lessons (can't remember the fella's youtube account but his name is Mark if I remember right) that are very good for beginning bassists.
Finally, your hubby should learn "the box" ASAP. With the exception of flashy solos by guys like Victor Wooten, etc., most bass playing is done in the box. Once you know the box and a few simple patterns and walks you can play almost any song that you know simply by applying the box to the chord chart and a rhythm pattern appropriate to the song. The exceptions are songs that have a very specific bass "riff" that makes the song - "Stand by Me" for example. "Stand by Me" is still played mostly in the box but because the riff is so distinctive you pretty much have to play it like the original or people think you're "doing it wrong." For most songs, though, just follow the chords with an appropriate rhythm pattern and you're golden.
One final warning - don't get too hung up on the blues walks. It seems like everybody and his brother has a youtube video showing the R,3,5,6,8,6,5,3 blues walk as if that was the holy grail of bass playing. It's a cool walk, but appropriate for very, very few songs even in the blues genre. You'll find a more generic pattern like R,R,R 8-5 much more useful in most modern western music. It's far less distinctive, but can be played over almost any style. I.e. it's a good meat and potatoes rhythmic device.