There are both pros and cons to allowing for the decanting of a trust. That is why you will want to sit down with an experienced attorney in your area that you trust to go over all the ways you can protect yourself and your beneficiaries in the documents that are drafted.
There are several ways other than trusts, for example, to bequeath assets to beneficiaries without the “manipulation” that you fear might come with a trust. These other ways should be explored and considered.
Forums like this are good for dispensing general information, by the way, but you will want all of the specifics of your particular situation personally reviewed by an attorney in your area. FreeAdvice is unable to provide personal reviews.