Where is the best shop/place to buy ipad mini, mid level watches (Hamilton, Tissot) and mobile phone

Fortress and Broadway are suggested and you can find their shops on the third floor of Harbor City in Tsim Sha Tsui.
It is not very cheap in Tung Chung. The two companies I suggested specialized on selling electronical applicance and they have reasonable price for all the applicances.

Thanks Alex!
how about mobile devices in Sin Tat Plaza second and third floor?

Is Ocean Park worth to go to with a 3 years old child?

Personally, Sin Tat Plaza at Mongkok, Kowloon is also a good choice to get the things you mentioned.

Don't worry! It is ok and nice for a 3 years old child to go to Ocean Park. But a baby stroller may need to be prepared for your kid.

Thanks Dylan. Hope this trip will be awesome. Thanks for all the valuable info