I think you are doing the right thing by not telling your parents. It is better to wait and present them with a 'fait acompli,' one way or the other. Hopefully, all you will have to eventually tell them is that your H and you had some problems and you've resolved them . If they comment now on something you can always say you are having a slump. All marriages have that.
Quote: Also, that the biggest thing for him is the big, giant empty feeling he has inside him
Your H is depressed. I do not know if clinically depressed, but big empty feelings that last months are called depression. Any chance that he'll get help? Just an idea...
Forget about whether H joins you in the trips or not. You cannot control that, anyway. Make your plans for you and your kids and enjoy!
"You don't throw a whole life away just 'cause it's banged up a little"
Tom Smith in "Seabiscuit"