From Benton to Lake Conway is about 35-40 minutes. There are also at least 4 other lakes within about that kind of drive. If there is a place for you to keep your boat where the grandkids live that would put you centrally located to having many options. There are also great Lakes that are just a little further drive, withing 1 1/2 hours. Ouchita, Degray, Dardanelle, Nimrod, Catherine, Hamilton ect, ect. Hope you can get the grandkids on some fish.
Chris