About the prenatal appointment - you should be fine to wait. My midwives don't see me for the first time until 10 weeks anyways. You should consider what kind of care you want and what kind of birth you are hoping for, and look for someone who is in line with your philosophy on pregnancy and birth.
If things are going to go wrong in pregnancy before 10 weeks, I don't think there's much anyone can do, really, and not much for them to check on yet anyways - the heart beat can't be heard yet, no measurements to take, etc.
Take your prenatal vitamins, eat well, rest as much as you can, and avoid the foods, drinks, and medications that are not recommended during pregnancy.
About the dogsledding - I really can't help you there! Ask your doctor/midwife when you get your appointment. Or do a google search.
OK, I just did a real quick search and came up with a story from a woman who went with her family while she was pregnant. All she said was that she wished she had another pillow.
Anyways, I'd still ask your doctor about it to be sure.
Congrats on the pregnancy and all the best!