The only direct flights are out of Atlanta, Miami, Houston and maybe Newark?. The Houston flights are Continental Red-eye's with early AM arrival on Saturday morning - only.
Insel Air just recently started several days a week out of Miami - I think they stop in Curacao first both ways enroute - it's a pretty small airport. American out of Miami to Curacao gets there early enough to catch a later afternoon/evening flight to Bonaire. Assuming you can get to Miami early enough. You should, we can do it from Phoenix.
So I think you're out of luck on the direct flights. Expedia or Travelocity should be able to confirm that from your choice of origin airports.
If you can get to Curacao by mid-afternoon there are several later flights on local carriers like Insel, Divi, or Dutch Antilles Express that do the short hop over to Bonaire. It's between $100-200 depending on the carrier. Divi has good service but really small planes, sometimes your luggage doesn't arrive until the next day.
Another option used to be American/American Eagle through San Juan but from here it required an all day layover in San Juan, A red-eye from here which arrived around 9am and the flight to Bonaire was around 6PM. It's possible that doesn't exist anymore, I had read somewhere that AE was eliminating a lot of their flights through the San Juan hub after the 1st of the year. But it's really the least desirable alternative.
All of the big dive resorts offer combo boat/shore dive packages so you should be able to get what you need. We bought 4 days of two tank morning dives but that was probably too much as the shore diving is so effortless and the sites are so plentiful. A good half dozen of the dive resorts are on named dive sites also and they all have facilities right on the water with easy entry via dive docks. So that might be an option also for easier diving. I shredded my shin about 1/2 way through our trip and after it infected, I just didn't feel up to the more difficult entries so for a couple of days we mostly dove the resorts. Or those sites in the south with small sandy entry points in the breaks in the ironshore.
Just about all the north of town resorts are setup that way, Capt' Don's Habitat, Buddy Dive, Sand Dollar Condos, Den Laman Condos, Eden Beach. The Divi resort is just south of town (walking distance to downtown btw) and the Plaza Resort to the south of town is on a divesite (18 Palms) also but their diveboats/lockers are on one end and the divesite is on the other end of the property. And it's a healthy walk. Sometimes you can get a ride in their golf cart, they use it to move tanks to the divesite.
Bonaire Dive & Adventure's dock is located between Sand Dollar and Den Laman, they're the house op for both and the dive site, Bari Reef, has the highest number of counted fish species in the Caribbean. Habitat is on two sites, LaMachaca and Cliff just to the north. The day we dove Cliff, it was an easy swim up and an even easier drift back. I've read Buddy's reef is also a good dive. So you can actually get in some good dives w/o having to go to the more remote sites with tougher entries. Most of the Bonaire sites are ironshore at the waterline or just offshore, there's smooth coral rubble in the surf line and no facilities of any kind. Pictures of a lot of them are here:
http://www.shorediving.com/Earth/ABC/index.htm
