Lease renewal strategy

[Kosh Vokter]

Tenant yearly lease expiring in June. Very good tenants, always pay rent on time, no hassles. they are asking if they could go month to month from July, since they are looking to buy a house and don't want to sign a term renewal contract. I would prefer to retain them as tenants, but also know summer is time of moving and so it might be harder to find new tenants, say if the current tenants were to move out in fall/winter. 

1. Can I ask for say 30? day notice and ask if they would be open to me showing property to new tenants in that 30 day window to reduce vacancy time?

2. Suggest a little higher m-t-m rent, than what it would have been if it was a term renewal.

How have you dealt with such situations in the past?