You're coming up to Haulover? That's really close to me and I would be interested in coming along with some equipment if its a go. However.. there is not a whole lot to collect in the area from my experience. Good place to sight some manatees in late spring and summer when the water is warm, I havent seen them at the canal for a few weeks now. (But I only check once a week, so perhaps I am missing them.)
Haulover is the main connection between Mosquito Lagoon and the main Indian River.. two of the smaller bodies of water that make up the IRL system.
Main catch from Haulover area: oyster crackers (be careful!), killifish, bay anchovy, mojarra (striped and spotfin), unknown gobies (two to five different types, some are enormous), catfish, juvenile sea trout and juvenile red fish, rockhopper orange blennies (unknown species), pipefish of at least three species but mostly gulf pipes, very very rarely Hippocampus erectus and even more rare H. zosterae.
For invertebrates: small hermits, larger mangrove hermits, blue crab juvenile and adults, spider crabs (esp. from rock outcrops), whelk / crown conch (not good tank inhabitants), and a gabillion zillion shrimp (grass, prawns, and more).
And of course, red black and white mangrove pods and you can get lucky finding Caulerpa prolifera, Acathophora, Gracilaria and other macroalgae.
That's a typical seine net day in this area.

You should keep an eye open for alligators. There are many in this area because it is part of the wildlife refuge land. These tend to stay in the hidden areas towards the interior sections of the mangrove swamps, but I have seen them out in the lagoon itself. Dont forget to do your stingray shuffle too!
>Sarah