what is the the cost ? Is grilling allowed? Are we able to stay over night in tents?

Camping and cabins are closed due to renovation. I think you can grill but the park is day use only for several more months.

$7/person/day

Very cheap to get in, few dollars/person. You can grill and they do have a camping area for tents. They also have cabins on a stream with bbq grills and kitchens for around $50/ night.