I think you need an opportunity to explore your feelings and talk this though with your OH, and with a third party, either on your own or with your OH.
It's a big step to take to jack in a relationship with the father of your children when there is nothing specifically wrong other than a loss of spark.
Relationships take a battering when our kids are young. We have no time or energy to invest in the things that keep a relationship alive and dynamic.
I know for several years when out kids were young we plodded along on autopilot, just one foot in front of another to keep us afloat and functional.
I suspect many couples are the same.
But relationships can ebb and flow, and joy can be found again when you have the space and energy, it is possible to fall in love again within the same relationship.
Part of your feelings may be a desire to fly, you may yearn in some ways for the times before you were anchored down by family life, when you were free and giddy.
There is no guarantee that you will meet Mr exciting, and even if you do you will still be juggling child rearing with a relationship.
On the other hand you may be right, you don't want to be stuck with this man for decades and life may be better if you seek new pastures.
No one can tell you what is the right path.
But I would urge you to explore your feelings deeply - speak to your OH, have some counselling, then at least you will be confident that the decision you make is the right one.