Hi,
You have a tough one here. If daycare isn't going to help with potty-training, you're not going to get there, so you need to talk to her. If it were anything other than daycare, I'd be saying switch, but obviously something so major in your life, that is important to your son, doesn't get switched so lightly.
You're going to have to talk to your daycare provider though, and find some happy medium, because you simply aren't going to get totally potty-trained on the weekends, and even if you can take him out for a week, and get potty-trained in a week, kids have accidents for some time after being potty trained, so you'd still face the same problem when he went back to school.
Once your son is fully potty-trained, things will be easier for your daycare provider, because she won't have to change diapers, so helping you is in her best interests. You can try to point this out in conversations, and also point out that if she doesn't help you, it will be a lot longer.
If your son was doing well at home, he may pick up quickly at daycare. You don't say if it was one or two days at daycare, or a longer period of time. But if it's only been a few days, I'd ask her for a little patience. Kids need to adjust to changes, and different levels of distraction, so it's natural that Monday would be different, but once he gets back into the routine of daycare, he may do better. She can remind him often to go potty, set timers to help her remind him, etc.
Personally, I even think that pull-ups over underpants would be confusing for your son. I'd be more likely to try purchasing training pants, which have extra thick cotton, and plastic pants, because he needs the feedback of feeling wet. There's also a product out there called pods, or something similar, that is an absorbent insert to put into underpants that feels wet, but limits the messiness of the accident.
My daughter potty-trained really quickly and easily, and she still had some accidents at daycare, including one or two poop accidents, (and we never had poop accidents at home after the first two days) for a little while. It's just natural until they get it down... so your daycare person is going to have to accept this eventually. Our daycare situation expected to and actively helped with potty training, although the "clean-up" only applied to the kids and the area... which is to say that they cleaned up the kids and put clean clothes on them, and obviously the floor, however the messy clothes were just tossed in a plastic bag and sent home. It was unpleasant at the end of the day, but if you are willing to accept this, it may make things easier for your daycare person, depending on how much she is expecting to have to clean up.
Best of luck!
A.,
Mom of Angelina 3 and 1/2 and Marley 5 months