Hi there, We have 3 kids ages 4,3, and 1, and we live in Tanzania, just outside of Arusha.
Congrats on your future move to TZ. I have never been to Dar so I couldn't answer your questions about schools, or prices around town. You shouldn't have any trouble finding a place that also accepts your dog. They really don't care about things like that here. But do check out what is required to get your dog in the country.
Also some other tips on moving here w/kids. Bring your kid stuff with you - for example a portable high chair, sippy cups, etc. Good quality kids things can be hard to find or just really expensive. And where ever your house it... Do go overboard on security, you don't want to take chances with your family, and it helps you sleep better. For ex. have a night security guard, make sure your house has a good wall/fence, things like that. Getting around can be crazy !!! In Arush a shopping day takes Forever b/c you have to go to one store for the meat, one store for the ketchup, toilet pater, etc. and them the market for the fruits/veg... and getting around town can take forever. But I think in Dar they have more normal grocery stores with more of everything in one store.
Bring a car seat/ and booster seat for your kids, those can also be harder to get here.
Make sure you filter, even the boiled water with a special fluoride removing filter. The water here in TZ has too much fluoride naturally and cause bone problems and dark spots on kids teeth. I believe the best hosp in Dar is Aga Kahn, but not for sure. But it really isn't even on the same scale as an American hospital, make sure you double check everything the Dr.s / nurse says, I have had a Dr. prescribe Cipro antibiotic to my 2 yr. old, luckily i double checked it learning that you don't give cipro to a child cause it may shut down their kidneys, and other organs. So anyways... yes there is medical here, not great, but adequate, just double check.
Malaria is a biggie here, children react different than adults when they get it, sometimes hardly no symptoms at all until it is very serious. I Always keep malaria med in my home cabinet, if i suspect it, i dont wait until the next day to get them tested, i start them on treatment right away, if you plan on being here long term, some dr's dont recommend prophylactics b/c the long term effects of the med can be worse than just treating it if you get it.
Sorry i could just ramble on a bit, I will not try to overwhelm you with the scary stuff all at once. :-)
You can email me and I can send you my little "mini book" about moving to TZ. EastAfricaMissions@Me.com
Take Care,
Bonnie TZ