Help with getting an iOS device

My only experience is a hand me down original iPad I received from a relative. I know next to nothing about their devices. Long story short, I need and Apple device that had iOS 11.0 or later and I was not sure what the cheapest route would be to get such a device. The cheapest I’ve found new is a ipad 7th gen for $279. I can find refurbished items cheaper but wasn’t sure if the savings would be worth it or if there were any significant jumps between specific models that would be worth spending a little more for. I could get a mini or an iphone also but those all seem to be cost more.

If you’d like to know the reason why, my daughter is a softball pitcher and the school has a ball that will send velocity, rotational and other data to ipads/iphones. I have 2 younger ones that could potentially use it too. The company doesn’t have an Android app. The data would be useful but I’m not sure if it will be worth the cost but wanted to look into it. I just wish they would make an Android app and I’m a little surprised that they don’t. Getting something used or a refurb would be fine but don’t want them to update the app and end up having something stuck on an unsupported iOS version also.