You could use any wheels that worked within your design...
as to sensors... electronics is all about accuracy and sensors of all types are off the shelf ready ... as they say no need to re-invent the wheel, there is a lot of robotic kits already on the market... adapt them to your needs.
If you are thinking of doing this from a fun to do electronics hobby ... that is ok...
But if you are thinking you will save money over the existing robotic mowers, you will have to get very lucky to not waste a lot of development dollar$ starting from scratch.
It would be easier to make a mower remote controlled... fully robotic, rather costly to finally get it right... for that I would stick with what is already developed... :smile:KennyV