We have been going to Bonaire for 8 years now, staying in a Timeshare we own at Buddy Dive. In all that time, we have done exactly 3 boat dives out of hundreds of dives (we usually stay for 2-3 weeks). We like shore diving best - do not have to get up for early boat, and you are mostly by yourself when diving (no mobs!). If you plan to do shore diving, be sure to get a good guide. I recommend "Bonaire Shore Diving Made Easy" by Susan Porter, which helps you find and navigate both marked and unmarked sites around the island. You can get it in most dive shops, including at Buddy Dive. Buddy Dives' dive operation is great, and probably most convenient for your location (pickup tanks and go north or south as the spirit moves you). It has a drive through tank pickup with rinse tanks, and free Nitrox upgrade. They also run daily 1 tank boat dives at 8, 10:30, and afternoon and a night dive on Tuesdays. They organize Salt Pier and Town Pier night dives which must be accompanied by a guide and permitted. There are two 3 tank "dive safaris" per week on their new boat to the north side of the island (not usually dived) and they can arrange east side (wild side) dives as well.
As for car rental, we always use AB Carrental (
AB Car Rental Bonaire - 100% Best Price Guarantee!), a local company with the lowest rates and very nice people running the operation. Their category 1 (beat up pickup with no A/C) is $144 per week which we usually book. Not located in the airport but will pick you up via pre-paid taxi if you pre-book. Their office is in the Plaza Resort, which is close to the airport. Not luxury but adequate. As for insurance, the full coverage recommendation is probably good, but expensive. If you have an American Express card, they have a coverage option for $25 per rental that includes pickups that we use, but you have to pre-register for the coverage and use the card for the rental. Other cards (Visa, MC) specifically exclude trucks. Saves a lot of $.
As for Bonaire vs. Curacao, we have done both and love Bonaire (much better and more convenient shore diving) and did not like Curacao that much. The night life and eating options are better on Curacao, with 140,000 permanent population, but the shore diving sites are VERY spread out, especially if you stay south and dive north (where the best shore dive sites are located). Most shore diving sites on Curacao have dive ops at the site, so you don't rent tanks at your resort or a single dive op unless you are booking a boat dive package that includes shore diving. On Bonaire, you book a package with a dive operator (which can be only shore diving, if you prefer), and get your tanks when heading out. The sites on Curacao were much more beat up (anchor drags on the coral, sparse fish populations from over fishing, etc.) than on Bonaire, where they take their Marine Park protection more seriously. Crime appeared to be much worse on Curacao, but does exist on Bonaire, as some posts have said. For instance, dive ops on Curacao have to lock up their tanks when not in use because Curacao has a recycling plant and tank theft if common.
Hope this helps. Enjoy your trip to Bonaire.