Here's a good map for planning your road trips for the portion of your travel after you leave Negril:
http://www.jamaicancaves.org/jamaica-road-map.htm
I'd suggest getting the Texaco Road Map of Jamaica once there - the above is just for pre-planning.
If you're going to Seastar for their Saturday Party don't forget that includes their all-u-can-eat buffet - I would not eat dinner before going.
You could still do Rick's to just watch/film the divers and have a drink or two while catching the sunset. It's actually a pretty good time and not that expensive given you are planning on just 1-2 drinks and going elsewhere to eat.
From Rick's you are a very short walk over to Seastar. Maybe can catch the end of their Happy Hour (2-for-1 for all drinks/beer), which lasts until 6pm - if you plan right. Between then and the start of the buffet/party - don't forget they allow you use of their pool even if just eating/drinking and not staying there - so don't forget your bathing suits.