On Sept. 8, we observe National Grandparents Day. If you have grandchildren, they will hopefully mark this occasion by sending a card, making a call or, best of all, paying a visit. But however your grandchildren express their feelings for you, you undoubtedly have a very big place in your heart for them. In fact, you may well be planning on including your grandchildren in your estate plan. If that's the case, you'll want to do the best you can to preserve the size of your estate - without sacrificing the ability to enjoy life during your retirement years.