We're going to Cambodia and Vietnam for ours in less than two weeks from now!
SE Asia is good because once you're there it can be as cheap or luxurious as you can afford. I've managed to get flights (inc internal) and accomodation in for a bit less than 2K, including staying in some stunning looking places.
Fly in to Siem Reap, chill out in posh hotel and go and visit Ankor Wat (you can cycle around the temples).
Fly to a deserted tropical island, stay in a $25 beach hut, eat, drink, moped around etc
Fly to Halong Bay, overnight in a Junk or somesuch boat sailing around huge islands of limestone towering above. Maybe do some Sea Kayaking (except I nearly died last time I tried that)
Hanoi.
Go home (boo!)
Book as much as you can beforehand if you're only going for a few weeks, rather than waste time once you're there, and don't leave it till the last minute, it's not worth the nagging, and you'll get sucked in to organising wedding stuff nearer the time.
Plus you won't have any money left…so book it now! :lol: