Desktop Mac or Laptop Mac?

Hi,

This is my first post in the Apple forums.

I have no background in the Apple Computer world. never owned one.

I do use a Nexus 4 now as my daily driver.

I own an iPad2 for my daughter which she likes very much and uses it comfortably.

I have a Sony Viao Windows 8 Laptop and an Old Windows XP Desktop (getting old)

I am looking to replace my XP Deskptop with Either an a) Laptop b) or a desktop.

I am looking to buy an Apple product this time as it is easy for my daughter to play on it and surf and use any apps.

I dont have any special requirements as my work related stuff is handled by my Sony laptop and all I will need is to surf the internet, transfer pics from iPad2 to computer and watch videos and maybe purchase some apps for my daughter (games or study related)

I am confused whether to go for a Macbook Air or Full fledged version of iMac (all in one)

can you guys please suggest me which is a better option?

Thanks.