Counteroffer confusion

[Plopster]

Am a seller with offers from 3 different ebayers.

Can I send all three of them the same counteroffer at the same time or is this risky?

Am worried split-second timing may come into play & if two accept at the same time, I will be unable to fulfill one of the sales.

Yes you can send them all the counter offer. Whoever accepts it first will get the item and he other parties will be informed the item has been sold.