I have been asked out on a date and I would like to go.
Do I tell him? So that I don't have to hide anything?
You're not asking if you should go on the date, right? You are asking if you should tell your H that you are going on a date.
What will you accomplish by going on a date?
Of course there are all the questions of what kind of date is this? just the 2 of you? a group date? a romantic candlelight date? a lets get a bunch of us together and go grab a bite to eat date?
That you have in interest in another man is information that really helps me understand how easy it is for you to say to your H you set him free. Man in the wings.