That is definitely doable. What will you put in the master bedroom in that large open area when you first walk in?

Redrawing the plan with wall thicknesses will help weed out many concerns. The more detailed the drawings are the more creditable reviews can be made. Also furniture laid out to scale and clothes hanging in closets help.

Show the layout of the house now and superimpose the addition so we can see how the whole relates.

Yes, I will put the master in the big open area when you walk in. I will work on adding the layout of the rest of the house.

Doable, and a cost efficient attractive functional result are totally separate things. Get thee to an architect. Immediately. You aren't understanding standard industry sizing for multiple things. The scale is all off.

An addition that large suggests the original house is fairly small. Which means that a teardown of the original is the best course of action. Do a larger new build that is a cohesive single piece. It is going to be more cost effective. And end with a much higher value.

The original house is around 2,000 sq ft. We are opening up the kitchen/living/dining area to create a much larger living room, dining and den area with three additional bedrooms and 2 bath that are already updated.

It's fun and easy to dream up a new floor plan, but an addition is more than the plan, it also needs to make sense, and be doable on the exterior.

Accurate measurements and an accurate drawing are also important. Sometimes inches matter.

Putting your ideas into a CAD program that does 3D will let you visualize your ideas and allow you to account for those pesky inches.

I'm sure there is free software available, but I'll recommend one of the Home Designer titles https://www.homedesignersoftware.com. Pricing starts at $130.

It's really helpful to see the as built plan as well, so we know what you are starting with, along with some images of the exterior, and any specific restrictions/wants.

A number of things I'd do differently, and I agree with an above poster who says scale is a problem throughout. I think you've let the anticipated square space decide for you what spaces are larger vs. smaller.

KITCHEN

- I'd 90-degree the island so that it would "play more nicely" with the sink /would create a nicer main work area. That would leave the refrigerator just outside the main work area and would allow someone entering through the pantry to skirt the main work area.

- A 7' island cannot support 4 barstools. The people in the middle won't be able to get in /out. You have a dining room RIGHT THERE, so I'd downsize to two comfortable bar stools /forget trying to feed everyone at the island as if it were Waffle House.

- I assume you'll enter the house through the pantry? That's a good traffic flow, but I'd like to see a door taking you through the laundry room /on into the bedrooms.

- I'd move the dishwasher to the other side of the sink /place it closer to the dining room ... easier to move dishes straight to the dishwasher.

LAUNDRY

- Dryers are most fire safe /cheapest to build when they're on an exterior wall. This is not a small thing.

- You have a world of space in the master suite and the guest room ... but the pantry and laundry look a bit cramped ... comparatively. I know I'd rather re-allocate more space to these hard-working spaces.

GUEST ROOM

- What bathroom will these guests use?

- Do guests need a walk-in closet?

MASTER BEDROOM

- I'd add a door turning the end of that hallway into an "entry" /remove the planned door to the master. I'd consider closing off the planned bathroom door /add a bathroom door in this "entry".

- Is that a 3' wide hallway? No, 42" is minimum. Consider, too, bringing large furniture into the bedroom through that hallway /making the turn into the bedroom.

- Definitely add a door between the hallway and the closet -- keep the door between the closet and the bathroom, if you want. With this much space, you can afford two doors to the closet. This would mean fewer steps between the closet and laundry, and it'd allow one spouse to enter the closet without disturbing the other who's in the bathroom.

- The bathroom is large but uninspired /doesn't particularly look functional. You've allotted a great deal of space to the sinks -- why duplicates? They're not all that useful. This toilet-in-a-closet doesn't work -- once you add wall thickness, it'll be less than 36" wide, which barely meets code, and you want a few extra inches for comfort in a bathroom. People install these toilet-closets in an odd attempt to allow multiple people to use the bathroom at once -- why? -- but, in this case, you're considering having one spouse in the bathtub and another literally sitting on the toilet right next to them. If you're that concerned with privacy, don't you think sounds will make it through? I'd like to see at least a small linen closet IN the master bath. Where will your shower tiles hang? Where will your bathroom trash can(s) be placed?

- The master bedroom is quite large, but the bed is on the short end ... and the pathway to the bathroom door is cramped. With all that empty space at the foot of the bed, no reason for that. Move the bed to the wider wall, and the spouse who sleeps on the right side won't have to walk arooooounnd the bed to reach the bathroom.