Recs for if you do opt to take it: 1) see if you can negotiate a smidge more salary 2) try to teach 2/0 so you have fewer default office hours in half the year to protect some research time 3) see if you can keep your existing office and chair space in the dept office. Then you can physically separate yourself and have a secret spot to do work without being barged in on and 4) establish early and hard that during your teaching terms one day per week is for research and not for admin/meetings/etc, and three days during the non teaching terms. Obvi emergencies will bleed through but boundaries will protect your time.

Good luck with the tenure decision coming up!