If you truly want to preserve the genetics, yes open pollinate them.
If you want to preserve the genetics, AND start making some crosses of your own, open-control pollination would be to your favor. By open-control pollination, I mean make every cross possible and label each cross. ie: two males (A & B) and three females (C, D, &E) will give you six different crosses = AC, AD, AE, BC, BD, BE.
Now your next step is much simpler, you can start to get an idea for what traits your plants will breed true for, etc. AND you haven't lost any genetic variety.
Your drawbacks are time, space, extremely careful pollination and coordination. (but who doesn't enjoy honest hard work?)