Here is an article on Effectively Managing Change. I have been in your shoes a number of times. If you're previous acquisitions have resulted in mostly positive outcomes for those acquired, you can use the previous acquisitions as examples. We have even brought in other to talk about the change as they experienced it and the benefits they found with their new parent company. Often times this helps put folks at ease.

SBeccue-
There are a lot of comments here and I agree with all them. I've been acquired and have done the acquiring. I belonged to a company that acquired 23 companies in 4 years.

A few things. The person at the top sets the tone! First, it is imperative that the CEO attend and present. If they do not, the acquired employees will receive a terrible message: This new company doesn't really care about us, they just want the book. Her/his comments should center on the mission of the company, the company customer focus,the culture,general high level performance numbers (revenue, etc)and then why the company was acquired the CEO's vision of why this is a good deal and the role the new company is expected to play. She/he should welcome them and be very enthusiastic. If you have a dynamite presenter within the Communication/Marketing area, you may want them to present along with the CEO.

Second, no one is thinking benefits at the first meeting. Everyone is thinking "what does this mean to me and what are you asking me to do?" It would be good layout a timeframe of additional meetings, similar to a curriculum, that would cover some topics such as benefits, salaries, performance systems, etc.

Third, establish a method, and many do this online, with a bulletin board where questions may be sent and answered. A bulletin board will allow others see the questions/answers. Be sure to protect confidentialy of the sender.

I could list a lot of other things, but we'd be reading all day. The comments on this board from my colleagues are excellent and I endorse what they recommend.

I hope you find this helpful,

Best regards,

John92