Need advice on types of transportation for end of summer Scandinavian trip

It is usually most efficient to fly right where you want to be, and in the end, it's usually not more expensive. For instance, if you want to see London anyway, your plan is fine; if you don't, fly right to Oslo or the airport closest to Harstad. Yes, these other options require a plane change, but as long as you buy it all on one ticket and allow a few hours for the layover, it shouldn't be a problem. It's true that there aren't many nonstops from Seattle to Europe, but with one plane change, you can get almost anywhere (some places will require two changes).

You should also consider open jaw (multi city) tickets, into one city and out of another (for instance, Seattle to London, and Stockholm to Seattle). To find these, use the multi city option on Kayak, airline websites, etc. Don't look for two one-ways, as that's much more expensive.

"Should we buy some type of rail pass beforehand or just buy point to point train tickets if we are only going to be visiting Norway and Sweden?"

This will depend on exactly where you intend to go in Sweden and Norway. Once you have an itinerary, we can help you determine if trains, buses, flights, a rental car, or some combination of these, are the best way to get around. If you are taking enough trains, then a rail pass is worthwhile; otherwise it's not.

When I went in 2003, SAS had a deal where flights within Scandinavia were inexpensive when added to my transatlantic ticket; see if they still do this. Due to the distances and lack of speed on many of the rail routes, as well as the mountains within Norway and between Norway and Sweden, flying is often the best and easiest way to get between places. Since I went, there are now some budget carriers competing with SAS, so the prices may be very competitive with the train.

It sounds like your #1 priority is Norway, but what is your #2 priority? You should ask your mother and see what she prefers, since this may be her only trip to Europe. Then structure your travel plans around those destinations. Usually Icelandair has the cheapest fares between Seattle and Scandinavian destinations--but not always. Definitely you want to fly multi-city rather than a straight round-trip. Also consider flying from Oslo to Harstad instead of taking the train.

From Oslo, trains go as far north as Bodoe, which takes 17-19 hours with a connection at Trondheim. I think you'll want to fly at least one way. North from there, there are buses to Narvik and maybe to Harstad. From Narvik, there is a direct train to Stockholm but it takes 20.5 hours. For flight options within Europe, you can compare prices at www.skyscanner.com. For bus and ferry info, www.goscandinavia.com will usually give you all the links, divided by region.

You could also consider taking the Hurtigruten up the west coast of Norway to Harstad. In that case, you might want to consider flying into Bergen.

I'd go as early in August as you can.

Thanks for the advice so far. Since I have posted this initial thread, I spoke with my mom and we have a clearer itinerary of where we want to go. We are deciding between flying from Seattle into London or Amsterdam for sure now. My mother wants to see both places and we were thinking of staying around 3-4 days in London and Amsterdam first and then flying to Norway. Her family is in Harstad but we don't mind going there toward the last part of the trip. Would it make more sense to fly into Oslo or Bergen and then take a boat trip along the coast up to Harstad? We definitely want to see the fjords but aren't sure whether we should do that first on our way to Harstad or if we should do that last and end up back in Oslo or Bergen? We are open to any suggestions because we are flexible on which cities we could visit in Norway and save money when we can if at all possible. Thanks!