Since you will be completing your cert dives in Bonaire, take advantage of the great shore diving opportunities there after you complete your certification. There will most likely be a house reef at the dive resort you are staying at, which will therefore likely have a fairly easy (probably mostly sandy, although Bonaire has some really sharp ironstone shores) approach. It's pretty difficult to get lost when shore diving - you go off in one direction parallel to the reef/shore and turn around at a pre-determined time/gas point (remember to do a proper dive plan and buddy check before you start). You'll end up right where you started or at least very close to it, and also very close to shore in case you messed up a bit and need to surface swim back.
Enjoy!
PS: If this is a trip put together by a dive shop, you can also see if there are more experienced divers who don't mind two newbies tagging along. Divers tend to be a friendly bunch, especially on a shop trip, so it shouldn't be a problem.
EDIT: Sorry, I sorta misread your original post. You were asking more specifically about boat dives. You will have a DM/guide with you (as well as everyone else on the boat) on boat dives in Bonaire, so you won't be off on your own.
