hi,Mrs.Hong,first welcome to Guangzhou. The transportation is very convenient,so you can easily go where you want to if you choose a hotel near the subway to live in. I suggest you choose to live in Tianhe distract in the center of the city, but the price is a little more expensive naturally.At the end of July,Guangzhou is very hot,and the sun is very strong,so you should prepare something like sunblocks,sunglasses and so on.
May you have a good time in Guangzhou with your sister.I can also recommend some fun attractions if needed.

Thanks Mr Robbie. How much is the taxi fare from the airport to Tianhe? Will it be convenient if my 80 year old mom who travels in wheelchair come with us? i will appreciate it very much if you can give places and food we should not miss put when in Guangzhou. thanks so much.

About 30 km ,cost about 100 RMB.There are also some airport fast road line buses which you can take to get to the center city directly,and various grades of hotels offered for you to choose from along the way.TO be frank ,taking your mum in wheelchair is not that convenient for traveling,however,if she comes,I think you can also manage it because the subway facilities for the disabled is perfect in Guangzhou which can take you to most of the places you want to.