Here would be my recommendation using the assumption that they are all highly successful and want to make a go of it.
Each investor ponies up a rather modest $500k resulting in a new cash infusion of $2.5mm. Immediately bring A/P current. Send a letter to everyone saying. "Hey we are the new guys we are all in and fully funding this company. Obviously, we think this is a great product and hope everyone will stay in; however, we certainly understand people's concerns and frustrations. Therefore, if you want a refund, please send a new request to [email protected]. All refund requests will be processed within five business days. As for production, we are spending the next 60 days finalizing the current production processes, hiring additional staff and yada yada yada. After 60 days we will provide a definitive production schedule."
Send this letter to everyone. Process all refund requests in five days. If I were in on this and sitting on the fence, nothing would assuage my concerns more than this action since it basically says 1) we aren't going to jerk you around 2) we are invested in making this work 3) our pockets are deep enough so 4) your money is safe