Sorry I can't agree with your comments about entering adoptive parents in a genealogical database being incorrect. I appreciate there may be legal differences in different countries but generally legally speaking the child is fully the child of those adoptive parents and no longer has any legal connection with any natural parents.
The legal status of foster children is completely different - they remain the children of their natural parents.
Assuming these children are adopted, then I think they should be entered - some of the information like date or place of birth may not be present of course. However the Instructions for this particular Project do allow for a birth date to be calculated approximately from the information given.