Is what is happening in the family home – the disappearance of money and possessions, the movement of objects, and the appearance of unknown sources of money – a result of jinn activity, magic, or an ordinary person?

What is mentioned in the question is strange, because among the jinn are the righteous and the unrighteous, and they do steal. However, it is established that devils do not open a closed door, nor untie a knot, nor uncover a vessel. This indicates that the jinn are not those who stole the money in the mentioned incident. A Muslim can protect himself from Satan with Ayat al-Kursī, the morning and evening remembrances, and by frequently reciting the Qur'an, especially Sūrat al-Baqarah.