That's right, there is no guarantee that a coin will be worth any particular number of dollars. The price floats according to what people are willing to pay, just like Australian dollars or the Euro or silver prices float against the dollar. The reason people pay for them is that they are easy to transfer, durable, and scarce.
If I were you I would start accepting Bitcoins as payment and offer the people you need to pay a small bonus (5%?) as an incentive to investigate. For anyone who doesn't want to you just sell some coins to pay them. Maybethe number of people buying from you and selling from you in coins will be roughly equal anyway.