Mineral rights and proposed Illinois solar farm

My siblings and I inherited 25% of the [severed] mineral rights on a 300 acre farm in the Southern Illinois basin. My research shows only a couple of old, dry wells, no current activity in the area. However, I was contacted by an attorney acting for a company called Birchfield which has evidently bought the land for a solar farm. Planning for this farm is evidently pretty far along, it is not just speculative. The firm wants to buy surface rights from us to allow them to put up the solar farm and have offered us a one time payment of a few thousand dollars. I don’t know much about solar farms, but from what I’ve been able to discover, the amount of power produce is considerable and land is often leased for 20 to 50 years with a percentage of the income to the landowners. My question is, wouldn’t this also be a possible agreement for mineral rights owners? I see estimates of land lease values of $200 to $2000 per acre per year in this area, and I wonder if a fraction of this amount for the mineral rights could be a reasonable fee. The attorney I’ve talked to says they don’t lease mineral rights. My thinking is that if their project is already going forward, they will have to make some allowances for our demands. Does this make any sense?