If your father has used a computer recently then using a laptop should not hinder him. With that being said, I recommend you use the same operating system your father is used to, if applicable. If it’s a Windows machine then the price can range from $200 and up.
I agree! Changing to another operating system would not be a good idea. If he's used to a Window's Machine, iMore has a sister forum called Windows Central You may be able to get some good suggestions there. Here's a link.
If he's been used to Apple devices, I might suggest an iPad. My Mother Inlaw used an iPad quite successfully until her death last year at the age of 86.
