I have used donor embies. I will tell my kids so they know they were "chosen"
I am more worried about saving unwanted babies than ensuring my kids are "true" siblings"
I used a sperm donor for both of my children, and am using the same donor for my third attempt. He was an anonymous donor at the time, and is not financially remunerated at all. Since the birth of my first child, we have been in contact in writing through the fertility clinic, and last month my family and he and his family met, which was really nice.
It is the law in my country that children conceived through the help of donors must be told, although I don't know how this would be upheld. Also, donors have to have their names and contact details on a register open to their 'offspring'. Everyone has the right to know who their biological parents are, as we all need to know our true identity. It is also very important to know for health purposes. It is not a good idea to keep this a secret. Counsellors can help with a lot of the issues, and help with ideas on how to explain the truth to your child.