This isn't a "gerund/infinitive" choice, but a choice of meaning. "To" means "in the direction of" and "for" means "so it can be used by". Both meanings are reasonable, and both prepositions can be used. So choose which one fits your purpose more closely. The expression "Leave something to someone" is the common expression used to describe bequests.
It is really up to you. "Leave to" is the common expression used for bequests, but "for" is good when you want to mention or imply a purpose:
I'm leaving my jewellery to my granddaughter. (Focus on who gets it)
I'm leaving my jewellery for my granddaughter to wear on her wedding day. (focus on intended use)