Is he going to Paris? There were some threads in the past about what to buy in Paris. A good idea would be to get something that's hard or impossible to find stateside. One that comes to mind would be Parfums de Nicolai. Very clasical French style, and relatively inexpensive too, also because they come in 30 ml small bottles as well (for 30-40 euros) - so it won't seem you're trying to bankrupt him. Ideas could be Odalisque (woody floral), Maharanih and Sacrebleu (more vanillic, floral oriental). but most are good really. The downside is that he will have to go to the exact store - there are a few spread over Paris, including a convenient one not far from the Louvre.
Iris, violet, heliotrope almost sound like the recipe for two Guerlain masterpieces: l'Heure Bleue and Apres l'ondee. You can find them in the states as well, but in places like Saks or Neimans. Both have recently been reformulated to be more iris-centric and less heliotrope oriented, but they are still good. Apres l'ondee only comes in expensive bottles, if I recall correctly. L'Heure Bleue should be available widely and in cheaper formats.
If the budget is higher, the possibilties are endless in niche territory, starting from Lutens. But if he's paying, it doesn't sound right.
For himself, he can check Chanel pour monsieur (regular, not concentree) and Dior Jules, which are not sold in the US.