It sounds like you are looking to reduce the administrative burden of having two Plans (if it's just a paperwork issue, consider asking your new Plan provider about going paperless or householding statements to consolidate notifications and forms).
You can certainly roll the entire amount into another 529 Plan for a single beneficiary without incurring any penalties, because you are rolling once for each beneficiary. You should contact the Plan in advance, however, to make sure you have the required paperwork in order completed prior to opening the new account and making the contribution. Explain what it is you are doing, and it will further give you an opportunity to ask the Plan any additional questions you might have, and the plan representative an opportunity to provide any tips they might have.
For additional guidance you can visit this Q&A.