been to both OLCC
with one caveat---some units at OLCC are older---so if nice, modern unit is important, then GV. But for your age group, OLCC has SO much to offer. My 9 and 5 yr olds love this place (just went this Easter).
From free kids movies each day in a "real theater", splash lagoon, other pools, pool games, putt-putt, beachfront at lake for building sand castles and looking for mussel shells to the 2X weekly campfire with sing-along and smores, it is the 5-10 yr old paradise. Plus, if you are going after June, the River Island would be open-which is going to be great water feature.
GV is nice, too, and has 2 nice pools---but too boring for my active kids.