Facetime

My little one has a tablet but it doesn't have a pre installed face time, my phone has broken pieces of glass on it so i need the kids to use their tablet to facetime with their dad, does anyone have any recommendations on what i can use it's a small kids amazon tablet nothing amazing it has a really small storage but it does what it needs to. I can't afford any memberships or anything like that so i need a kid safe app for them to use for video chats. Money is extremely tight so any ideas are really appreciated thank you