I agree with @marciano; although think that it is usually a better idea to give them phantom equity rather than real equity. Phantom stock is essentially a deferred compensation plan that is linked to performance.

I've been on the sell side of many deals in the low/middle market. This subject always comes up because it can be an enormous business risk. You need to be flexible and you need to talk to the current owner(s) about it. What would motivate the current employees to stay on board? Sometimes you don't have to offer anything but mitigating the uncertainty of the current employees is of upmost importance. I almost never suggest a cash bonus immediately after close. If an employee is going to leave you can't stop them no matter what and you probably didn't want them anyway. What I often suggest is offering benefits (or better benefits) and a 12 month retention bonus / performance bonus. 12 months will give you a good read on the value of each employee. I would almost never suggest giving any sort of equity away.