For those that use formula and send LO to daycare, how do you pack the bottles and formula? Do you mix them beforehand? or pack them separately?

One daycare I looked at said they will not mix formula so I'd have to send the bottles already mixed. But I thought they were only good for 2 hours after mixing?

We will be starting with a small home daycare next week and she's willing to do it however I want. I'm thinking about just leaving a canister of formula with her so she can mix the bottles herself.