Jeff, I'd give yourself 3 -4 hours from Liberty to AC if you're taking the intercoastal. Figure 100+ miles at 45 mph with no wake zones, maybe a train bridge, the canal etc.
The outside all the way down would be much shorter if you're up to it. It takes about an hour to an hour and a half to get from Sandy Hook to Barnegat Inlet and less than an hour to get to AC inlet from my recollection.
I've never made the trip all the way from Sandy Hook to AC but have done the trip from Sandy Hook to Barnegat Inlet countless times and also did Sandy Hook to Beach Haven, NJ but did Brick NJ to AC on the poker run.
Have fun, sounds like a nice trip!