Car services with child seats
We used Eastern for the first time in a while recently, since we weren't bringing our own car seat on a recent trip and they provide a car seat for the kid. They were punctual and courteous, and their system sends you a text message ahead of time with a description of the car and the driver's name and phone number so you know what to expect. My only complaint is that you don't actually get a price quote when reserving online, but the price was essentially what we expected each way. They're a little more expensive than Dial7 or Carmel, but they seem to be the cheapest option that offers child seats.
Another option with child seats is Legends (legendslimousine.com). They're a little more expensive than Eastern but offer a really slick online reservation system that gives you an instant price quote, and their cars are generally a little newer and fancier. I haven't used them personally, but have a good friend who swears by them, so I wouldn't hesitate to recommend them to someone who wants a child seat with a slightly higher end service than Eastern.