Valerie,
I suggest you wait and revisit your options after July 2018. At that tine, you may be inline for a long term royalty stream, be able to lease again with a lease that benefits your long term plans, or reconsider the advantages to you lifestyle by finding a buyer that want to trade cash then for a long term involvement in your acreage. All of these options are most likely better than the offer to sell now.
One situation you should avoid between now and July 2018 is the granting of a top lease or anything that reserves your mineral rights for a date past July 2018. Demand for acreage in your area will only get stronger in the next year. Use that to your advantage.