I will give the foster child a choice. Do they want Android, or iOS. This answer will be important for them, as this will decide the device they will receive for the next 5 years of their life. With that said, I will do my best to make sure they have a competent tablet. If they choose Android, it will limit the options they have. The only quality tablet maker I know of is Samsung. With that said, I will give them an 11″ tablet which will be Wifi only, but there will be a micro-SD card slot that would support up to 2TB cards. The tablet will also include a stylus which will be good for writing notes, or drawing.
If they prefer iOS, then I will likely give them an iPad Air 11″ model, and give them a stylus. While there is a cellular version, there is no version with microSD card expansion. In that regards, Samsung is a better choice. The child will not receive a cellular version. If need be, they can always use their cellular phone as a modem, and use that to connect to the internet. No matter which tablet they choose, the child will be able to take the tablet with them when they leave my custody.