Acknowledgements are good. And here are some great rules to follow when writing them:
If you're a writer, one thing I recommend is that you keep a Word file called "Acknowledgements." Whenever someone beta reads, helps you with research, encourages you to keep going, or otherwise contributes to your writing, make a quick note of who did what (and for which book, if you have more than one project in the works). Make sure you thank everyone involved with the business side of getting your book published, including your agent and your editor, as well as anyone who works for these folks who makes a significant contribution, like the copy editor who spends twenty hours catching those last typos in the galleys.
It's not hard, and the people involved will cherish it.