TO - Those behaviors we to do our children such as punish, criticize, slap, etc.
FOR - Those behaviors we do for our children that they could have done themselves. Or, those things the child did that we didn't find good enough and did over.
WITH - Those behaviors we do with our children such as vacations, sports, activities, a good visit or an activity that is pleasurable for all.
Which one makes the memories? Which one builds relationships? Of course we can always manage to make any event miserable with the way we behave or take things personally. Often foster children misread situations and react with oppositional or angry behaviors. We always explained activities in advance - where we are going, what we wear, eat, where we sleep, hours of activities, behaviors expected and not allowed, etc. We build in as many "what to expect" instructions as possible.
The answer to the questions above? WITH - but you probably already figured that out.