Sounds like you've found a great ortho, with loads of experience in what you want to do. Ask if any of his staff have had linguals and talk to them about their experiences.
Kissing with linguals will be noticeable if your hubby has a tongue that likes to explore. But they won't hurt him, as long as his tongue isn't aggressive!
With 'straight on' kissing, you'd not be aware of a person with ibraces, as most people don't notice brackets on the front of the teeth.
If you're certain you want orthodontic treatment with linguals only, then hopefully before long you'll become more confident and this will be a great experience for you!