Cakes and Desserts - Rainbows and Racecars

My middle child's 3rd birthday is in two weeks, so I need to get planning!! He loves rainbows so I wanted to do the inside of his cake like this:

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More frosting like above or less like this one?

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But the theme of the party is race cars.

So I need to do the top something like this:

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Love the simplicity of these two cakes:

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Or I could do an open rainbow cake with a racecar on top:

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 Or this theme was mixed beautifully here:
(minus the wiggles theme)

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And of course I will have to do a colorful candy buffet to match!!

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So many fun ideas - so little time - wish me luck :)
I can't wait to post all of our pictures from the party - I will keep you posted!