His response, you know I'm no good at planning, I will mess it up.
This response sounds familiar to me.
My wife is an introvert and a homebody. I'm an extrovert and an 'adventurous' type. I'm pretty much down for being out and about for anything at any time (particularly true before we had a kid). My wife also enjoys getting out and having adventures, but she is more particular than I am.
She has also complained (at times) that she feels like she is the one who always has to plan things in our marriage, that nothing would happen if she didn't take the initiative first. And that's true - I have stepped way back from taking initiative on planning outings and adventures and trips and the like because I started to feel the same way as your husband - if I just went out and planned something, I would somehow mess it up (in her eyes). She is the picky one with constraints and standards and a busy schedule with her family and what not, so I have stepped back from just putting things together myself. If it's her idea to begin with, it's much easier for me to take action.
It's a little like sex - if I know that my initiating sex is likely to be met with rejection or resistance or complaining or criticism, I'm going to stop initiating. But when I know that I have a partner who will be enthusiastic and excited about my taking action, I'm much more likely to feel free and confident initiating, and it will happen more often.