I am actually in the process of helping a client do this now and have done it before. I am happy to connect.

When I worked at a nonprofit we did this.  We gave a 3 month notice and kept that notice going to really help people remember to prepare and save if needed.  Note if the health insurance pays will have to come out differently or double up.  I think we split that into a few pay cycles so it wasn't so hard on staff (it's been 12 or 13 years ago).  Overall, our transition was met with some grumblings but they were happy for the notice.  It was the best decision!  Gives a little cushion to correct any issues. Good luck!

To add... If you have the ability to permit a one time saved up vacation/sick leave or PTO time  (not to exceed a set time, like 40 hours or less) to help with the burden, you could offer this.  Just an idea...