I think if both of you are on the same page then you can explore ways of addressing this but splitting is radical when it may not fix anything.
I think midlife is a time we evaluate where we have got to and lots of people have that feeling of should have done x y z. There's no point wondering about how it would have been.
Outside of abuse situations, most people split because they want someone else. This doesn't sound like what it's about for you.
I would go to couples therapy perhaps to talk this through...if you can find a good therapist.
I don't really agree that a relationship is limiting. I am a single parent. THAT is limiting. I have not had the opportunity to do things that lots of my friends have in their relationships.
It sounds like there's still mutual respect but you both agree there's been a bit of a rut? Do you or your husband want other relationships or is it about the travel and personal interests? I think some therapy might help you identify a way forward.
As a long term single person, I can see both sides if it but it's a beautiful thing when I see my friends or family in life long relationships where they have supported each other and grown together with shared goals.
I think there are a lot of options but splitting up if you still love each other seems a waste especially with children to think about.