Hi there
We also started using wi/wo with our 13 month old dd and have been using this method for approximately 3 weeks. It has been going well. We are still not 100% there yet, but we keep trying
I did wi/wo for both naps and bedtime. My opinion is that you should do it for both as the main thing is to be consistent. If you are doing something different for naps then bedtime, or vice versa, you aren't being consistent. Hang in there :-*It may be a little rough in the beginning, but you will be glad that you stuck with it.
The main thing is that you dh will need to be consistent with this approach while he is watching him. If he isn't, you won't get the results you had hoped for.
HTH's and let me know how things go