Do I have to tell potential tenant about future construction?

[Nik Moushon]

I have a house on the market. Its a large house on .48 ac. The zoning that it is in allows for it to be short platted, which I have that process already started, and I will be building a Duplex on it. The process (surveys, permits, design) will not bother any tenant but construction will probably start this fall. So two question:

Q1 - Do I need to tell (put in the contract) future tenants what I am planning on doing in the future? Splitting the lot and building?  Since they are renting the house, that currently has .48 ac, but in 6months or so will have only .24 ac. 

Q2 - Assuming I have to tell them, what exactly do I need to tell them and does it need to be in the contract or is verbally enough?