I’ve been unhappy to varying degrees for a long time but I’m mainly unhappy because I don’t feel equal in this relationship and I don’t feel brave enough to stand up for myself.
You don't necessarily owe it to your partner and kids to stay in the relationship, however I would say - so long as there's no risk of violence or abuse - that you owe it to them to at least try and sort it out. You say you don't feel brave enough to stand up for yourself - one way of looking at what your planning is this is just another manifestation of that very issue.
Your obviously feeling unheard - but do you actually know how your partner would react if you actually asked for what you want? Or is he assuming you're good with everything because you make out everything's fine? Because, if so, this will repeat - you're not fixing the part of you that can't ask for what it wants. You're simply running away to avoid having to do so. To avoid being brave and stating your own needs. And, IMO, that's unfair - not the leaving in-and-of itself. And if you state your needs and they're ignored, fair enough. Leave. But at least you'll all know what wasn't working and the culpability will be his.
If not, your partner will be left thinking "what the Hell did I do wrong?" In which case, no, he won't get over it short-term and find someone new, because he'll be stuck going over and over that unanswerable question, unable to trust himself in another, because, in his mind, his seemingly happy partner just bolted for no apparent reason.
Apologies if I've got the wrong end of the stick.