How to transition to whole milk?

My sons has been breastfed his entire life. He takes a bottle and sippy just fine. I’ve given him a bit of whole milk to see if he would drink it and he doesn’t seem to mind it and it doesn’t seem to bother his stomach. When he’s at home with his dad or daycare he only drinks 2, 5 oz bottles of breastmilk, one in the morning and the other in the after noon. Since he seems to tolerate the whole milk now do I go about switching? Do I give it til him at the same times he drinks breastmilk? Do I only give it to him with meals? When do you offer water? Do I start with milk in a bottle and then switch to a sippy cup or just give it to him in the sippy right away? He doesn’t seem to be attached to the bottle. I’m running very low on my freezer supply and wanted to get him transitioned before I run completely out just in case he decides to fight the transition and I would still have back up breastmilk. He’s also just switched to a new daycare and I’m afraid all this change is going to upset him ☹️