BSnape - As others have said, if you end up going to Tahiti you will not be able to leverage SWUs all the way through to PPT due to the AA metal requirement.
A few years back, my wife and I took a trip to Tahiti (loved it & would definitely recommend it a 1000x over) and were in a similar situation with SWUs - we had one other Int'l trip that year where we used 4 of them, but had nothing else planned due to the time/cost of the Tahitian trip so were looking to burn the last 4 SWUs there.
We are ORD based so we flew ORD-HNL on AA metal. While this is domestic flight, we used the SWUs to guarantee our upgrades well in advance of the trip. Personally, I don't think ORD-HNL is a bad redemption - it is an 8.5 hour flight which is 2+ hours longer than it takes us to travel to most European destinations from ORD. While I could have played the EXP upgrade lottery on these flights, my wife would have been SOL not being AA status so SWUs were nice for piece of mind and also to get my wife upgraded.
Once in HNL, we flew Hawaiian Airlines from HNL-PPT... if I recall correctly that was maybe a ~6 hour flight from HNL. Hawaiian Air is an AA partner so you can earn or redeem miles there. We attempted to try to use miles to upgrade on that Hawaiian Air flight - I don't recall if it was due to availability or the redemption rate was just horrible, but we ended up not doing that and just flew coach.
Personally - I would pick where you want to go for your honeymoon and make the SWU work. Don't pick your honeymoon destination based upon the longest AA metal flights that are best use of SWUs. If you do choose to Tahiti you would not regret it I can promise you that.