I got my first chicks ever about 5 weeks ago, so I know how you feel. I obsessed over the temperature of the brooder (it was fine), putting marbles in their (ACV treated) water, extra grinding on the food, visiting the post office (twice, she thought I was nuts, but she called me at 5:30 a.m. when they came in), paper towels over shavings -- you name it, if someone on this list mentioned it, I researched it and iimplemented it.
The girls are doing just fine. We got back from a day trip today, and I went out to the run to sit with them for a while. They were jumping all over me. Angel (one of the 2 Delawares) hopped on my shoulder and tried to eat my hair, and Lisbeth (the usually shy Welsummer) jumped onto my knee and told me exactly how she felt about being "abandoned" all day. Welsummers (or at least mine) have unique voices that really get across irritation. Woodmort is absolutely right. Relax and enjoy them. They don't stay tiny very long. Make good preparations, test the temps in advance, then sit back and enjoy th babies.