How do I use FindFirstChild?

When I use the script below, it only changes the MaxActivationDistance of one ClickDetector. I want it to do it to all the ClickDetectors it can find inside ModelA or at least on that level.

local a = game.Workspace.ModelA
local b = a:FindFirstChild("ClickDetector", true)

function onClicked()
	script.Parent.ClickDetector.MaxActivationDistance = 0
	wait(0.5)
	script.Parent.Parent.Base.Beep:Play()
	wait(1)
	script.Parent.Parent.Base.Beep:Stop()
	wait(0.5)
	if b then
		b.MaxActivationDistance = 0
	end
	wait(2)
	script.Parent.Parent.Off.ClickDetector.MaxActivationDistance = 32
end

script.Parent.ClickDetector.MouseClick:connect(onClicked)

I understand I'm not explaining it very well but I can't really explain it any better.

Thanks!

local modelChildren = game.Workspace.ModelA:GetChildren() --the children of the model
local ClickDetectors = {} --a table to put the ClickDetectors in
local ready = true --a debounce, so it must finish before it starts again.

function onClicked()
	if ready then --if not in progress
		ready = false --make the script know it's in progress
		for i, v in ipairs(ClickDetectors) do --these three lines change the activation distance for all click detectors.
			script.Parent.ClickDetector.MaxActivationDistance = 0
		end
		wait(0.5)
		script.Parent.Parent.Base.Beep:Play()
		wait(1)
		script.Parent.Parent.Base.Beep:Stop()
		wait(0.5)
		for i, v in ipairs(ClickDetectors) do --same as before
			script.Parent.ClickDetector.MaxActivationDistance = 32
		end
		ready = true --finish the function
	end
end

for i, v in ipairs(a) do --this is what puts the click detectors in the table and connects the event.
	if v:IsA("ClickDetector") then
		script.Parent.ClickDetector.MouseClick:connect(onClicked)
		table.insert(ClickDetectors, v)
	end
end