Forget anything you think you know about what they want and like.
Because that is guaranteed to be WRONG.
And WILL result in bleeding.
If you like your skin, teeth and hair where it is NEVER take them to Toys R Us with you. It is quite literally like attending a dog fight, but with vicious midgets, Iggle Piggle and Fisher Price branding... *winces* Learnt that one the hard way... And remember, just because they like it in the shop, does not mean they will like it when they get home. This also applies to people. Well. Daddy. (But then he can be a real twat sometimes.) Also. No matter what you buy them, your handbag still kicks the shit out of all of it. *whispers* I put knives in mine now... they don't expect that...
Please be aware that the exact lifespan of a toddlers interest in AN-Y-THING is exactly 2 minutes 37 seconds. And goes like this. 'Ooh shiny... Ooh a box... Ooh something in the box... Not edible (slight nibbling to 'check'), face of mild disappointment... Ooh makes a noise... Wonder what will happen if I shit all over it and feed it to the sofa... Right bored now... NEXT!' So think about that when deciding whether to buy them a iPad, or hide a slightly browned satsuma in a used sock... I'm an fruit-in-footwear girl every time... As a real treat, perhaps put all the 'red' quality street which no-one else likes in their stocking too. Along with some string. Lucky bastards.
I suppose what I'm really saying is just give them money. Then when they are not looking, take that money and buy yourself some f@*king vodka. And a Toblerone. And a vaginoplasty.