Your solution makes three erroneous assumptions:
1. That they haven't made any admissible contradictory statements prior to their trials.
2. That a jury would believe anything they say.
3. That both of their attorneys will violate their ethical obligations by putting them on the stand to lie.
Unfortunately, Craig and Kelly both gave statements on Dec.15th.
And without an attorney in Boston, they likely gave additional statements upon their arrest.
You can be sure that by now, they have given contradicting statements - statements that contradict their own earlier statements AND statements that contradict each others' statements. That should be enough for a jury to completely disregard their testimony and enough for their lawyers to be committing malpractice by putting them on the stand.
Special "Arnie Becker" Ed