I do not work in your market, nor do I know your relocation company's policy, which should be reviewed before you respond.
That being said, there are a number of options that you have, and your relocation company and Realtor would be the best sources of advice.
Generally speaking if you are in a buyers' market (where there are more homes than buyers), you have a couple of options:
1. Reject the offer
2. Accept the offer with the sell contingency
3. Accept the offer with a provision that the buyers need to lower the price of their home a set percentage per weeks until it sells. 1% per week might do the trick, although 2% might be better. Most homes that do not sell are overpriced.
4. Accept the offer with the condition that it be "Right of First Refusal". That means that you agree on a sales price, and also the condition that you will continue to market the property, if another offer comes in then the buyers have 24 hours to remove their sell contingency or you will take the newer, better offer.
You can see that each one of these has pros and cons, so discussing these with your Realtor and Relo company is a must.