What's your reasoning for wanting to?
The kindle fire is great because a) its comparatively cheap at £50 and will allow them to use it for much, much longer than say a leap pad.
B) you can set a time and function limit so it automatically turns off after a set time and you can easily prevent it from accessing Internet/non-child friendly media.
But... Why does a 2yo need one of their own? At that age I was happy for mine to use my tablet occasionally.
The elder 2 turned 6 and 8 this year and have only just got their own kindle. The youngest are 4 and the only reason we are considering one for Xmas for them is because it will save fights over doing homework on the apps school use and because I can restrict its use better than I can on my iPad. Weirdly they are happier with the kindle suddenly switching off access when their time is up than by me setting a timer and removing it.