[Bonanza]

If you sell your property with a lease in place, by law, a new owner must honor the terms of the lease.
You can ask your tenant if they would be willing to find another property to rent,
but they are under no obligation to do that since you already have a fully expedited lease.

Tenants can make it very difficult in showing a property that is for sale.
In a case such as yours, where it is rented as a seasonal rental,
your tenants are basically renting it like a vacation property.
They may not be agreeable to making it easy for showings,
particularly with spur-of-the-moment appointments,
and probably would not like having a lockbox on the door.

You really need to discuss your situation with your tenants before doing anything else.