I’m a mother to a toddler (I sometimes come here to gain perspective).
I have a somewhat similar arrangement with my MIL. She watches my son once a week for a few hours. I don’t necessarily need her to, but she has offered. I say yes because I appreciate her wanting to spend time with him and a little time to myself to do other things is nice, too. It’s a mutually beneficial arrangement.
I won’t say you’re being unreasonable, but here is where your DIL may be coming from.
-toddlers have a much easier time with familiarity. My son naps better at home and most importantly sleeps better at night when he naps at home. Every time he naps or sleeps at my MIL’s I have a more difficult time getting him to bed at home afterwards. Sometimes, his sleep is thrown off for days after.
-packing up a toddler is a lot more stressful than an adult packing themself up. Even if grandma has some supplies on hand, I’m still going to pack his bags and end up walking in there if a bunch of stuff. Getting him to the car with all his stuff is a headache. A lot of the benefit for me is lost because packing and moving him, itself, is so stressful. Sometime I dread going anywhere (even to see friends) because the logistics of going out with a young toddler requires so much extra effort. Then we have to unpack him when we get home and figure out where everything is, put it back in place, etc.
-my home may be smaller than my MIL’s, but I know it’s childproofed to my child’s needs. My MIL’s home doesn’t have gates on her stairs, locks on the drawers, an unsecured china cabinet, furniture isn’t bolted to the walls, etc. I have a harder to being away from him when he is there because I’m worried about what he could get into. You
May think that’s overkill, but it’s natural for a mother to worry about her child’s safety.
I understand the preference to be in your own home and that you don’t like having to drive to her, but if you’re truly trying to help out, going to her is probably most helpful. Could you talk about splitting the arrangement? One week in your home, one week at their home?