The M54 engine does indeed spec the LL-01 rating. The M52 (2.8l) was good with the LL-98 but when BMW decided to stretch the interval out to 15K, they upped the spec.
I would recommend a few. First, use the BMW "High-Performance" 5W-30 synth from the dealer. Its shown good numbers on analysis, is readily available, and is reasonably priced. In fact, if your B-I-L is a BMW CCA (Car club of America) member, he can get a discount. Second, if you can still find the "German" Castrol Syntec 0W-30 in the 04 batches, I would recommend that also (its what I currently use). Third, I like what I've seen from others using the Mobil1 0W-40. Its good for LL-01 and is ACEA 03. Whichever he goes with, I would also recommend to go to 7500 miles. Do an analysis and go further if he feels comfortable, otherwise dump at that time. Alot of Bimmer folks are doing this with the "free" maintenance BMW offers. Fits nicely in between the 15K interval and puts some fears to rest about going that far on the oil.