If they were there before 1910, go with the 1910 census first. The 1920 census I have found to be lacking when I was looking for people. Scroll through to where you want to be and yes look on both 1910, and 1920, you never know what else you will find. The census was usually taken in June, this was the time when most places were accessible. Also remember the 1918-20 flu was going through Alaska at the time, just in case anyone is missing. Also birth and death records were local until 1913, when these records were first recorded with the Territory of Alaska government. Up to 1900 and maybe 1910, there was only three judicial districts( Juneau,Fairbanks and Nome).
Hmm, if the 2nd child was born in 1901, there must have been twins or a child almost every year till 1910 or so. How did you get the 1910-20 census so quickly?