I assume you mean that you are aiming to sing a high G which is at the top of your vocal range? I think I can allow that.
Can I make a suggestion, though. I had a similar problem trying to sing El Condor Pasa. The arrangement I had needed a high G (coincidentally). Though I could reach the note, it was pushing it. In the end I tuned the uke down a tone (to Bb tuning - F Bb D G) which meant I could play the same chord shapes but sing it a tone lower so the top note was F rather than G. I found that worked well as you got the same chord voicings and the lower tuning actually gave the uke a more mellow tone. Think about it.
If you go for the separate voice and accompaniment, can you lip sync the final video? It should look OK then.