Have driven through this park as we like to go over to the jetty in Nokomis right down the road and it is a cute park. I don't think we felt like fishing would be great there (but was just very surprised at all the tilapia we landed in Myakka river SP)
Most of the FL SP have really decent restroom facilities so your black tank should be OK, consider washing dishes like we do sometimes using the outdoor shower on our TT if we are without septic for a few extra days
If you want to continue hanging around FL in April take a look at Stringbreak at the Sertoma Youth Ranch just up the road...it was an outstanding music festival last year & we are now thankfully grandfathered in to our site (forever I hope)
Camping since May 2013 .... FL & GA only so far .... loving it!