I think Grandpa has a mighty narrow view of life. Civilizations exist all over the world and with the internet bringing Singapore into your home, I feel it best to get to know something outside your own four walls.
I too have parents who live only 20 miles from where they were raised, and their first reaction was, "are you sure you want to do that?" They still refuse to come visit, but I am damn glad we did this, after all we are the ones who are living our lives, not them.
You will never regret making the decision to live overseas. The new friends you will make will last a lifetime and the experiences you will have will be priceless. The children will learn that Sacratomato is not the center of the universe and that sending Grandpa and Grandma letters, pictures and e-mail (assuming they are online, or are willing to become if they want to keep in touch) is great fun. There are numerous different cultures just on this island with several more available for exploration for cheap money airfare to destinations nearby.
Purely for the sake of not regretting passing up the opportunity in later life, go for it. The pursuit of the dollar should be secondary, the opportunity to expand your world and know and understand someone other than fellow Californians should the your primary priority!
There, you wanted my opinion...right 
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Paul N.
He who dies with the most toys...is an idiot. Family First!!!