Are you using a bottle for feeding or just a medicine dropper? In June, my husband and I took in 3 orphaned baby kittens that a friend found and didn't know what to do with. When we took them in, they hadn't eaten properly in a couple days and one was shaking and barely moving.
In my bedroom I have a large bathtub, that I lined w/ blankets and towels and put a heating pad in the corner under a couple blankets. I put that on medium (it has a shut off after 2 hours also) and placed the kittens on it with a couple fuzzy stuffed animals and it kinda gave them something warm to cuddle on/up with to keep their body temps up. Kittens need to be kept warmer then older cats, but I am betting you read that already :o)
Also about the feeding, if you haven't gotten a kitten bottle, I would recommend it! It makes feeding soooo much easier, especially when they are eating more as they age. I used one bottle for the kittens and had multiple nipples for the bottle that I switched between feedings, and the kitten bottle is labelled w/ oz & such so I could track what each kitten was eating. I also used a food scale to track their weight and made sure they were gaining. As for the stimulating kitties to use the bathroom, I used a washcloth w/ warm water and stimulated over the sink for easy cleanup.
The kitties do get messy but remember they need to stay warm. I wiped them down with a warm washcloth, wrapped them in a warm towel for a few & rubbed their fur dry as much as possible,t hen used a blowdryer on low to dry them (from far away so I didn't scare/burn them) and then returned them to their cozy heating pad/stuffed animal area.
The kittens I had made a ton of noise! If they weren't sleeping, they were crying for milk and to be loved. The benefit of this...I now have the most loving kitten ever. It is so amazing to watch them grow. When I got the kittens, their eyes were still only open a tiny bit...and within days they opened nice & wide, and they started walking versus the little stumbling around they were doing the first day. Within the first week I moved them to my large open closet and used a baby gate to keep them in/other cats out...until after another week and a half they learned to climb the gate and jump out when they were hungry! I had to set alarms at night to feed them every 3 hours, and I work from home so I was able to feed them often during the day too.
I lost one of my little kittens at 5 weeks. The vet didn't really have an explanation but at 3.5 weeks I had rushed this kitten to the vet because he was lethargic, not eating, not using the bathroom and just sickly, and after being dewormed he perked up for a few days but then got sick again...it was horrible and I still get sad thinking about the little guy but I try to remember that it does happen and I did the very best I could raising the babies.
A friend of mine adopted the little girl kitten when she was 9weeks old and I still have the other one. He is the sweetest kitten and is so big and fluffy. He sleeps on my pillow at night, purrs constantly and SO loud, and follows my husband and I around. He is never very far from us, and is a total lap kitty. Bottle feeding a kitten is a great bonding experience, and even the kitten my friend had that I bottle fed is super loving w/ her new family.
I am certainly no expert on bottle feeding baby kittens but if you have any questions feel free to send me a message! Good luck & you are awesome for taking these babies in and caring for them!