Since these two are huge pullers,do not use a choke collar at all.I use one once in a while.BUT it's not to correct any pulling cause my guy isn't a puller.Ok that didn't make sence.LOL
These two need some serious one on one training.And somehow both you and your fiancee need to find time for this.And work at it.
You say you have a good sized yard.Well you can start there.Do some "walking" training.
You can try the harnesses.Some dogs take to the halti,some don't.Some will try and fight it.You can give it a try.
Have you tried contacting a trainer?