Are the two of you dead set on becoming involved with others simultaneously? Trying to coordinate a seamless transition for you both will likely be anything but seamless. Building relationships is not like putting the potato salad in the fridge until the chicken comes off the grill.
Either I missed it, or you didn't state directly the reason for the simultaneous start up (though I likely just missed it). Is this to avoid jealousy issues if one has an SO and the other doesn't? If so; what happens if you manage -by some miracle- to coordinate meeting people and it doesn't workout with one of you? Would the other one have to cut it off and start over? Maybe I read too much into it and this isn't the case, but this approach will present you with many hurdles.
Trying to get one relationship timed and following a schedule is unreasonable, two is just impossible. It would be great if we were that predictable (well, not really) but the odds are stacked heavily against you.
Just my $1.00 - 98%.