Lawn Mower Recommendations Needed

We live on a piece of ground that has been in the family for over 100 years, our section is approximately 6 acres of lawn, all flat. The senior family member used to handle the mowing but since he is now 99 years old, it was time for him to retire. He always used Craftsman mowers and the last one is just about done.

So, what should we be looking at as a replacement?
Thanks