Definately a northbound trip IF Denali Park is a priority for wildlife viewing (the most excellent area for this). You need an arrival there after June 1 for the shuttle system, or the end of May for the "tour" buses to get far enough into the park. BUT- in my opinion- group tours on a fixed schedule by bus are NOT ideal with a child and way too costly for what you get. Also consider going on your own with perhaps 2 rental cars. Would allow far more touring options and the ability to see what is YOUR interests. Head to your library and take out Alaska travel books, especially Foddor's Alaska and Frommer's Alaska. Also take a look at THE MILEPOST, a necessary reference for independent touring. IF you still want to go with a cruise tour- go for at least 7 days interior- any shorter has too much time in transit compared to what you have at the destination. For the wildlife- you need the Tundra Wilderness tour not the Natural History tours BUT if going BEFORE the last week in MAY ALL tours will essentially be the Natural History as the road isn't open. Be very very informed of what you are purchasing- I find descriptions vague- the rail is 8 hours Anchorage- Denali Park- so have 2 nights there. Via bus about 6 hours. Meals are extra except where listed on the land tour.