Like the others who have chimed in, your bikes - both the FI and carb - will run fine from sea level to the mountains. If you are into racing or wanted every ounce of maximum performance out of your bike then minor adjustments could be made or adding a fuel processor and such. Since you are cruising you will be fine.
A windscreen will help a lot in making your ride more enjoyable. After all that is what this is all about. I have a National Cycle Switchblade mounted windscreen on my 900 Custom and it works just fine. Being a Switchblade model I can remove it without the aid of any tools. I didn't want the windscreen to dominate the bike so it isn't very tall, but it works just fine for me.
I have the Kuryakyn Ultra Tour Bag for my long trips and it works great. The zippers are covered with a rubber strip to help keep rain out, but it does come with its own rain cover. It has 4 outside compartments and a single large interior compartment. It has D-rings so you can strap it to your seat or use the velcro band to go around a backrest/sissy bar. The straps on it have cam type locks so it is very fast to put on or take off your bike. Thus I can take it inside to a hotel or tent if I am camping. I like it better than the more expensive Grand Tour bag. The 4 outside pockets are pretty good in size. I have them divided up into functions like tools, rain gear, bike cover, spare parts. The interior compartment will hold my clothes and other needs.
A Clampbuster (for about $6) is a great investment to alleviate cramping in your throttle hand/wrist. I also have a mechanical cruise control - Vista Cruise - that I use when I need to let go of the throttle and give my arm a break. I don't really engage it for very long but its handy. I think it cost about $30 and took about 30 minutes to install. The Clampbuster (check cycle gear or any other bike place) took about 30 seconds to install.
Get good rain gear. The cheap stuff will shred quickly at highway speeds and leave you soaking wet. I ride with a leather jacket, chaps, boots and gloves. For pop-up thunder storms or light rain these work just fine and dry off rather quickly at highway speeds. If I have to travel in a healthy downpour I break out the frog toggs and stay nice and cozy and dry.
I still have my stock seat and really really really really need to get a different one. However, I got about 175 to 200 miles and then fuel up. This helps with the TB syndrome (tired butt) but I will get a new seat when the funding permits.
Just a general note on taking long trips. Check your oil level when you stop for the day. I have a small mechanics mirror that extends and I attached a cheap subminiature led flashlight to it so I can sit on my bike and check the oil level. Check your tire pressure each day before you start out. Take time to stop and smell the roses. Its all about the ride.
Have a great trip.