hi luckystar78sg, I have thought about this thing as well.
for the top up from sapphire to ruby package, you need to pay the exact price difference between the 2 packages. The prices will be the same even though if you are holding on a Fri/Sun night.
After much consideration, I have decided against the top up as it will be very rush for Fri/Sun night dinners. I have attended a number of Fri night dinners. Most of them started only at 830pm, one started as late as 9pm.. The whole thing was a mad rush... The above experience are not applicable for GPCH, as i have yet to been to WD @ GPCH where such packages were taken up..
you might want to take my advice into consideration. =) cheers.. Look for William, he can advise you accordingly.