Hi, Pls let me share my experience here, while my former employer was going thru due diligence process by a potential buyer, my management awarded cash bonus plan letter to selected group of key employees by offering them an opportunity to share in the success of the combined business grows. Personally I was preparing to leave the company knowing the potential sale but stayed back just because of this cash bonus plan letter. Hope this helps.
You could also do a small raise at closing (which may keep people around longer-term than one payout might). I’m also thinking about light-weight benefits we can use as retention mechanisms. For instance our company has unlimited PTO and many that we have looked at acquiring do not. This or other things like access to training, participation in ERGs or sending company swag might be small, low-cost ways for key employees to feel included. I also like the suggestion in the training of having them take on small integration projects to stay engaged and valued.