I have been to Bonaire a few times and it is a fantastic flat water sailing experience with 80 degree temps for both air and water! Lac Bay generally has onshore winds with a large mostly shallow sailing area and is one of the best beginner intermediate places to learn in the world. There are a ton of advanced sailers here as well so expect to see some of the worlds best freestyle sailors.
kumamovie.com/kuma-in-bonaire-2016/
In the past I've been in months of February, March, and April with winds typically high teens to low 20's. We've had days that are higher and one year that required dipping into the fleet of 7+ sized sails but mostly sailed between 5.5 and 6.6. I am about 190 lb and tall so I am typically on bigger gear than most. Check the wind by month charts to see data.
I went to Aruba twice before going to Bonaire and I think the sailing is better in Bonaire. Aruba has more to do in the evening and larger chain resorts, I think the Vela Windsurf place is right next to three different Marriott properties, but the wind in Aruba tends to be slightly offshore and little bit more of a trek in terms of getting out to the wind while bonaire is on shore wind which translates into more sail time!
Bonaire also has fantastic shore accessible snorkeling and scuba. Everyday you could drive to a different beginner friendly site and not need guide and still be able to see interesting aquatic life.
We've always rented from Jibe City which I think typically has slightly newer selection of gear and friendly staff. If you are teaching kids, I think the Windsurf place has better kids beginner gear as Jibe City only has trainer sails smaller than 4.0 while the Windsurf Place has some kids Maui Hot Sails rigs, but otherwise we favor Jibe City, but we've never tried Windsurf Place. The Windsurf Place site shows photos of some newer RRD gear. I don't think that was there last time we were here. We might be splitting hairs here since both shops gear is relatively new, but my memory is that Jibe City tends to refresh their gear more frequently so it tends to be slightly newer.
The more simple answer is that the sailing in Bonaire in February is going to be way better than the weather in Chicago!