What do you think of my mash up?(Heart Vacancy and Happy Ending)?

At school we're having a talent show. My friend and I (both 13) are
entering as a duet. I play guitar and sing, she plays piano and sings.
My friend wanted to do Heart Vacancy by The Wanted, but I wanted to do
Happy Ending by Mika. I realised earlier on today that they can both
be played using the same chords, so I thought I'd try and do a mash up
of them.
Here's the link- http://vocaroo.com/?media=vXqD9Sa1E4BrSopQF
I have a cough, so there are a couple of mini pauses in the song where
I've been trying to hold my cough back. (The cough will be gone in a
month, when the talent show is on).
And I can't help but change the tune a bit, I hate it when people copy
songs exactly!
What do you think?
The bit at the end where both songs are sung at the same time will be
split between me and my friend, like
This is the way you left me, (In your heart, in your heart, in your
heart,)
I'm not pretending. (I can tell you can fit one more.)

I'm thinking of doing a bit in the middle where I sing the 'little bit
of love' part of Mika's song, whilst my friend sings 'in your heart'.
Do you think that would sound okay?
And I'd only practised it once before I sung it, so if I practise
every day, it'll sound a lot smoother.