Hi Prashun
What a beautiful tabletop that is going to make!
I can only echo the advice so far. The gap looks larger than it is simply because it is doubled when you slide the two pieces together. Obviously the ends of the boards need to be taken down first, before one long, full shaving is taken from the length. Check this with a straight edge.
The hard bit is determing where you start/end the end cuts. I would mark the carefully, not plane in the general area. Take a very fine shaving when doing this - better that you take more shavings to get to the desired level than drop further than you wanted.
Don't you wish you had my 36" jointer now! You are welcome to come over and borrow it!
The thickness of the timber is my concern. It will move if not dry. The joint may open. I would be ensuring that the support for the top allows movement from the centre to the sides. What plans have you made?
Regards from Perth
Derek