Hi MzTrudi,
If the dispute is just about the tablet, it is best to speak with the father and negotiate with him directly. Does the father know how much it is upsetting his daughter? Perhaps he really wants to use the tablet for himself and is a bit addicted to it. Unfortunately, father's can sometimes be selfish and put their interests above that of their children. Is it possible to get your daughter another tablet and leave that one with him? Or work out a time share arrangement with her father?
Although having a gift taken away from a 7 year old is understandably very upsetting for you and your daughter, in the scheme of things it is probably more an internal family matter rather than a legal dispute and it would be best dealt with between you, your daughter and her father. Remember it is more important to maintain your daughter's relationship with her father than have a tablet.
However, if the issue runs deeper than a tablet, you could think about
mediation with the father or reaching out to a
Family Relationship Centre.