We started out our 4 month old with the Salus Bijoux after many miserable drift/sail/motorboat trips in other "infant" life jackets. What a brilliantly designed PFD! It was amazing how much more our daughter relaxed and enjoyed the rest of our summer/fall trips! It's also great because it has the mesh back so she could sit comfortably. It's worth the cost and waiting for it to arrive from canada if you plan to use it in the first year!
If you do wait till next year then the Stohlquist Nemo is a wonderful PFD once your child is up and moving!
It's tricky because the Salus Bijoux goes to 25lbs and the Stohlquist Nemo has 0-30 and 30-50, so if you get the Salus, you have a 5lb gap to jump to the Stohlquist!
Good luck and way to plan on getting out there!