I would combo an iPad and a wireless keyboard. You can get ones that will allow it to sit on your lap like a laptop if you wanted, but have the flexibility to use it as a tablet as well. Since you already have the iPhone, all your data will sync and allow you to switch between the two devices if you wanted. Plus you would not have to repurchase any apps or subscriptions you already have on your iPhone. You also do not need the newest version, you can get them pretty affordable by buying off a year or two, or buying used if it is going to be a farm use take some wear and tear anyways.

Example Hybrid Case:
https://www.amazon.com/dp/B08M6GMT6T