Guidance for shooting US Capitol in backdrop from rooftop wedding

I am not a pro and also first time user of this forum. I am hosting a wedding rehearsal dinner party this month in Washington DC on the top floor of a building with a patio landing that is open to the sky and looks right at the US Capitol. Very iconic image. We did not hire a photographer to shoot at the rehearsal dinner. We will be facing east and the Capitol is facing West meaning at 6pm the setting sun will be shining bright on the Capitol. The Capitol is about 300 to 400 hundred yards away in a straight line which means it is a very wide image at that distance . A number of the guests will want to shoot a photo on the patio of themselves with the Capitol as the backdrop. They will be using their cell phones and you may say their modern cell phones will take a better photo than my D100 with the NIKKOR 24-85mm lens. If so then please say that.
I could set up the D100 on a tripod and use it for shooting them with the Capitol as the backdrop. If the D100 will add quality over a cell phone, my question to you is what settings should I set up on the camera. I need to plan for the subjects to be (1) in full sunlight or (2) in filtered light or shade if the slight building height above us blocks some of the setting sun from their faces, meaning only the backdrop of trees and Capitol is in full sunlight. They would be looking into the camera with the Capitol to their back. Therefore I would want the people and the Capitol to be in focus.
The D100 has a built-in pop-up flash if needed. This is the link to the D100 specs. https://imaging.nikon.​com/lineup/dslr/d100/
I appreciate any guidance.

it is extremely difficult to get a good pic when the subjects are looking into the sun, which is what the set up sound like. They will be squinting against bright light.

If you can put them in shade that would be better, but i suspect they will be underexposed and the capitol will be overexposed. With this set up the pop up flash is likely inadequate to make much difference but might help a little. Speedlight would be better to fill in a little. A proper strobe and softbox would be best.

and yeah, with the built in single exposure HDR of most newer phone cameras, often they are better set up for this shot ... from an exposure perspective, if not a sharpness and overall quality perspective.

Thanks for the quick feedback and advice.

Left Handed Brisket wrote in post #18877626
Speedlight would be better to fill in a little. A proper strobe and softbox would be best.

Additionally, you can take some bracketed shots for HDR in post.

drmaxx wrote in post #18877972
Additionally, you can take some bracketed shots for HDR in post.

Bracketed shots of humans? Never tried it but seems it wouldn't work due to subject movement.

Might be able to get creative with positioning in the frame, I guess.

Left Handed Brisket wrote in post #18877991
Bracketed shots of humans? Never tried it but seems it wouldn't work due to subject movement.

This is an issue, but if you have the group posing then there is a good chance for success - if the automatic HDR fail, then you still can take the well lit pic with the people in it, apply a mask and blend in the background. Clear lines in the background help.

Will the shots be taken into the sunny or shadow side of the dome? This makes a huge difference. I used to take this sort of photo every year with the Illinois capital building from an adjacent rooftop. The best bet is to slightly underexpose the building and use fill flash to expose for the humans.

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Great feedback, much appreciated. Per your question of dome, we will be shooting east into the west facing side of the capitol (building + dome). Since we are high up on a office building terrace it is a phenomenal vista into the Capitol that is 300 to 400 yards away. Assuming it is not overcast, the Capitol will be bathed in sunlight. We are so close that we may not be able to get the whole Capitol in a backdrop group photo.

Left Handed Brisket wrote in post #18877991
Bracketed shots of humans? Never tried it but seems it wouldn't work due to subject movement.

Might be able to get creative with positioning in the frame, I guess.

If Leapyr explains what s/he is doing, it may work. If people stayed still for daguerreotypes, I imagine people can stay still for less than a second for an HDR shot now. A 7D2 can do 10 shots a second, other cameras are near that speed.

Maybe OP can pick up a few of these:

http://thephotopalace.​blogspot.com/p/head-brace.html?m=1