Different things are going to work for different people depending on the details of the use case.
I am quadriparetic, and have personal aides who come to the house. One of these has house keys. So we have experimented with various different things.
For us, The simplest has been to use the combination of a special mode and zigbee presence fob. It sounds like that might work for you also. Still have the cleaners use their regular keys. But the fob should detect them sometime between the sidewalk and coming through the front door. Its presence should then shift you to the “maids are here” mode and you can control the lights then however you want to. Then when they leave, The fob moving out of range can change the mode back to "away "or whatever you want.
You can also set this so it only runs at certain times or on certain days of the week.
I know you indicated a concern about battery life. Ours looks to be on track to last about a year, which seems fine. It should last a minimum six months. If you get it and it drops very quickly, then it’s probably a defective unit and should be replaced. You will be able to see the battery level in the smartthings mobile app, so you can arrange for the replacement when it gets down to about 20%. worst case is you have two fobs, and have them take the replacement and leave the old one when the battery level is low. (Or you could have them leave the fob with the low battery, manually change the mode that day and the next time they come, and replace the battery and leave the fob for them to pick up, although that takes more synchronization.)
Anyway, if you’re already trusting them with the keys, I think the presence fob is worth considering.
But whatever devices you choose, having the special maids mode is what really makes it work.