He could buy 0.1 or 1 BTC with same effect. Why he bought exactly 2 BTC for each kid?
Lol,

why do you insist on questioning the unimportant? We can only assume their opinion, if you want to get an accurate answer try tweeting at RFK's twitter.
Everybody has their own reasons for buying Bitcoin and everybody has their own reasons
to sell them again when the time comes.
Yes we have to understand that reason because not all reasons can be revealed, each individual can still keep a secret why buy 2BTC, why not more, then if he is rich why not buy millions of dollars of bitcoin, this is not important at all.
Maybe he bought 2 for each of his children so that they could sell one at a later date
and still have 1? who knows exactly?
It could be that they can sell it all at once when the price is high, or it could be that this is just for their political purposes later.