I had this same problem when I went to PNG on a dive trip two years ago. At the time I was living in Japan, and my doctor (German, at the local expat clinic) said he wouldn't prescribe Lariam for divers. Which suited me, after the various scare stories. He wanted to prescribe doxycycline - this is also what the Australian doctors in Cairns etc recommend to people going to PNG.
But doxycycline has a couple of disadvantages:
1) you need to start taking the tablets 1 week before, and continue for 28 days after. 1 tablet every day - this is one area where Lariam has an edge
2) it is quite a powerful antibiotic, which may be ok for the guys, but can lead to unpleasant side effects for the ladies, as it can cause thrush. I've had vibramycin for a throat infection, which is doxycycline by another name, and would prefer to avoid a repeat. Particularly if going to a hot, humid, tropical country, thank you very much much
3) and, again more for the ladies, but no doubt also of more than academic interest to their partners, doxycycline can interfere with the contraceptive pill, so anyone relying on the pill needs to switch to/add another form of birth control while taking it.
So, having done my research, I asked "what about Malarone", and he agreed it was a good alternative.
As well as relatively few reported side effects you only have to take Malarone tablets two days in advance, one a day while you're there and for one week after leaving the malarial area. Disadvantage - cost. It's much more expensive - it was about $10/day I think, though I can't remember if it was AUS or US $. Still, cheaper than dealing with side effect 3) above
methinks.
Only problem, it wasn't available in Japan. So I had to get it sent out from the UK. And I'd just like to thank Lake Pharmacy in Cairns for filling my prescription urgently when the post didn't arrive in time! Of course, I then had a spare fortnight's supply when it did turn up, so I just had to organise another dive trip to PNG.
Have a great trip, whatever you take. remember, while lariam may be contraindicated, malaria isn't a good dive buddy to have either!