How to decide 2 or 3 frozen embryos to transfer

Found out 1st IVF didn't work.  Now on to doing frozen transfer.  We have 6 embryos frozen.  Was told today that one of those was in its hatching phase so that is good.  Dr. said that most will transfer 2 or 3.  Really don't want triplets but after having 2 transferred this last time with it not working I'm now wondering what to do.  Hubby says 2 so that is probably what we will do.  I just went online and it looks like frozen transfer is only 20-30%???  Is that what you've all heard?  That just seems so low.  
Now waiting for period so can start birth control pills again.  Also was told I will be taking Viagra suppositories every 6 hrs for 1-2 weeks-never heard of that-anyone else doing this?  Supposed to bring blood flow to the uterus.  
Also after transfer I heard to eat pineapple-any other suggestions?  Doing accupuncture and have cut out caffiene.