There is an article on traveling with babies/toddlers in the current Cruise Travel Magazine. Most important would be, to be certain the ship you choose offers babysitting. Few 1 year olds can tolerate multicourse extended dining if you plan on this. (you can eat all your meals at the buffet however??) Also be prepared for excursion limitations and think carefully about what your priorities are for Alaska??? I would think a balcony would be a must?? As for route- you if aren't doing an interior tour- I would recommend a round trip Vancouver/ Seattle. 6 out of 7 days are the same on round trip and one ways. The long and possibily overnight flight from Anchorage- again may not be well tolerated by that young of a child??? OK as for your route question- I prefer southbound- great last sailing day back to Vancouver loaded with marine wildlife viewing opportunities- probably not of great interest for you, as it requires a great deal of time parked out on a front deck with binoculars??? If you do go with a one way- I highly recommend a trip that includes College Fjords.
I guess it's all preference because I really liked the northbound sailing out of Vancouver. We had family member who went southbound, and they complained about having to wake up at the crack of dawn on the last day of the trip to sail into Vancouver, which is a lovely port to sail into. (Nobody likes disembarkation day anyway, so that doesn't sound like fun to me.) We sailed on Princess at 5:00 p.m., so we got to see a lot of the scenery before it was dusk at about 10:30 p.m., but there was probably a lot that we missed that was referenced by Karen 16. I do think the northbound or southbound are much better than the roundtrip because you get to see so much more. I also loved the College Fjord/Prince William Sound area.
We liked the northbound route because the scenery just got more and more spectacular the farther we went. Glacier Bay and College Fjord were beautiful! Some people will tell you that they wouldn't do a one-way without spending several days interior pre or post-cruise. We didn't have time for that but are still glad we went one-way. There is so much we wouldn't have seen if we hadn't gone all the way to Anchorage, e.g. wildlife.