you would have to split the amount you want to buy in smaller transaction, and even when that's the case you might still attract too much attention. Most of the exchanges out there have limits, the limits I know of are about 15 - 20k USD per week/month depending on the exchange and country. Different countries have different regulations and it's easier to do the transactions in some than others. If you want to trade higher amounts than that you will definitely have to find a corporate specific broker and try to legally buy them (you'll have to submit tax records, etc.) a lawyer would be a good idea in that case since you're talking about over half a million dollars (100 BTC).
He will be needing legal adviser in this case since it is a matter of a lot of money. Too many bitcoins are not easy to buy at a time. The current price of bitcoin is very high and are highly expected to rise by the end of this year and because of this you need to buy bitcoin from different exchanges by involving your lawyer in this matter since you need to prove your identity in order to buy large number of bitcoin.