Tenant breaking lease-no clause in lease

[Jennifer Hollander]

My tenant informed me today that they will likely need to move out by November 1st due to job relocation.  They are current on rent and have 'offered' their $750 (equal to a month's rent) damage deposit in hopes of that being considered alright and a clean break.  I'm rereading my lease and realize that I don't have anything in there in regards to breaking the lease (yes, my failure). What I DO have in the lease is the following:

END OF LEASE. The Landlord asks that the Tenant provide a 60 day notice, in writing, of intent to evacuate the premises.

Based on that, can I hold them to a 60 day notice or rather two months worth of rent?  They have been good tenants and are going through some custody issues at the moment.  This rental is in an area where it is in high demand, being a 3 bedroom.  I'm fairly confident that I can turn it quickly in November.  December could be another story with people spending extra for Christmas.

We prefer to allow them to break the lease with some term of fair agreement as I prefer not to drag this through the courts since I feel we can rent it quickly. I'm just not sure what is legal and fair. They've only been there 4 months and I will actually contact a couple of people that were  highly interested before.  I appreciate any help and I will be redoing my lease to state that there is a 2 month penalty for breaking the lease.  Thank you!