Unfortunately, under the circumstances you describe, if the funds make their way to your churches, what is at risk is the churches' tax exemptions.
I don't have any magical way around doing what you want to do.
There are all kinds of intricate rules to prohibit just what you're suggesting.
There's a "doctrine" potentially in play called a "step transaction" where if an interim step were employed, such as donating to a friend's church or other not-for-profit organization who then passes the money on to your church in whole or in part via a series of transfers, in effect what happens is that only the first and last "steps" are considered, so it becomes the same thing as making the contribution to your organization directly.
Any "loophole" that exists will have to come from the provisions of the Trust. Anything else, where you and your sister's organizations wind up with the funds will put your respective tax exemptions at risk.
Sorry, but I've done a lot of work with not-for-profit organizations and you must be really very careful that you don't do anything to benefit any director or officer of the organization with money donated to the organization unless it is for legitimate services at reasonable rates.