Where is Camp Kikiwaka?

Nowhere, since it is an imaginary place.

However, the fictional location of Camp Kikiwaka seems to be near to, probably within easy walking distance of, the fictional town of Moose Rump, Maine,

According to IMDB, the camp is at Moose Rump Lake, possibly a take off of Moose Head Lake, the largest lake in Maine.

Fortunately for the campers, Bunk'd is a comedy, indicating that Camp Kikiwaka is probably nowhere near spooky Maine towns like Collinsport, Cabot Cove, Derry, Salem's Lot, or Castle Rock.

I think that the first season episode # 113, "For love and Money", the 17th episode aired, was the one where the store in Moose Rump was by docks, so Moose Rump should be on the ocean, a big lake, or a large river.

I think that the second season episode "Fog'd in", number 212, the 31st episode aired, had Zander. Lou, and Emma walk to a lighthouse, indicating Camp Kikiwaka is close to the coast - maybe that was "Mud Fight" # 216, 17 March 2017.

In "Mother May I?", episode 210, the 34th episode aired, Christina Ross visited Camp Kikiwaka.
A list of Bunk'd episodes says: "Christina Ross arrives at Camp Kikiwaka upon the yacht that she and Morgan own being in the area".

The yacht that Jesse and the Ross kids used in a Mediterranean vacation in the three part "Rossed at Sea", the Jesse episodes # 414, 415, and 416, the 89th, 90th and 91st Jesse episodes aired, on June 5, 6, and 7, 2015, was a rather large yacht. It looked about 15 to 20 feet wide, and maybe about 100 feet long.

So I doubt that Christina's crew would sail that yacht very far from the ocean.

And in the Bunk'd episode "The Great Escape" number 213, the 42nd episode aired, Ravi, Tiffany, and Jorge go for a hike in the woods and get lost. And they eventually find themselves at a crossing point on the US-Canadian border, and have to persuade the border guards to let let them cross back to the US side. I expect the kids probably walked less than five miles to the Canadian border.

And I don't see how they could cross a bridge over a large river on the border without noticing it.

And the crossing place has to be close to the seashore as "For Love and Money", Fog'd in", and "Mother May I?" indicate.

The St. Croix River Runs into an inlet of the ocean that is part of the border, and makes a bend at the towns of St. Stephen in Canada and Calais in Maine. I believe the Ross yacht probably docked somewhere below the bridge that is at Calais and Christine took other transportation to Camp Kikiwaka.

The area has two lighthouses, But I don't remember anyone mentioned taking a boat to St. Croix Island in "Fog'd in". The other one, the Whitlocks Mill lighthouse, is in Maine, at the Narrows of the St. Croix River, a mile or two southeast of Calais.

http://lighthousefriends.com/light.asp?ID=505

Thus Camp Kikiwaka and Moose Rump are probably in Washington County, Maine, a few miles from Calais, Maine.

So far so good.

But maps indicate the St. Croix River, the border between the USA and Canada, is not narrower than about 300 feet anywhere within about ten miles of the Whitlocks Mills Lighthouse. And I doubt that it would be shallow enough to wade across anywhere along that stretch.

The St. Croix River was chosen as the border for many miles by the Webster-Ashburton Treaty of 1842. Since Bunk'd is part of the Disney Channel Live Action Universe, and thus happens in an alternate universe, it might happen in an alternate universe where after the Maine-Canada border was settled by the treaty in 1842, and everyone got used to that border, an earthquake or something moved the St. Croix river into a new channel some distance east or west. And the two governments decided to keep the old border in the now dry former bed of the St. Croix River.

So the kids walked down into the former river bed and up out of it without realizing what it was since a lot of trees had grown up to obscure the view (except in a 20 foot wide strip kept clear along the border, which the kids might not have recognized as more than a logging road or something). Moose Rump might be on the sea coast or the shore of one of the local lakes, possibly enlarged by the hypothetical earthquake.

06-20-2018 upon further thought, I think in the alternate universe of the Disney Channel Live Action Universe the border between Maine and New Brunswick is probably a straight line from someplace on or near the ocean running due north. Thus the kids wouldn't have to cross any rivers to accidentally enter Canada.