This is an awesome chain of lakes which includes the Dora Canal (a local favorite). While there is certainly enough mileage available for overnighters, the proximity to civilization (and private homes) really suggests to me a better opportunity for daytripping than camping. Lake Griffin State Park just down 441 does offer campsites, however.
I generally put in at Lake Eustis on the Tavares side, however there is very nice access on the Eustis side of the lake. There is also public access directly to Lake Harris off SR 19. I have never used this access and am not sure whether there is a fee for that site. I like to start with Lake Eustis since from there I can paddle the lake until I want a little shade and then slip into the Dora Canal (just off the Tavares public access under the 441 bridge).
The Dora Canal is just under a mile of pristine, "Old Florida" paddling. It's well shaded with lots of wildlife. I prefer the canal during weekdays however, as the motorboat traffic on weekends brings in a not so lovely smell of gasoline and scares most of the critters off.
To the West of the Tavares public ramp is the entrance to the Dead River which connects directly to Lake Harris. There are many canals leading from Lake Harris to some beautiful local homes but currently the low water levels make some of them less than navigable. Continuing south across Lake Harris you can connect to Little Lake Harris and some even quieter paddling.
I like this chain of lakes when I am up for some mileage. Most of this water is NOT shaded or protected from powerboats, so it is not a great choice for anyone uncomfortable with large wakes or wet-exits in deep water. Though I've never been tipped over by a boater on these lakes, there is always the possibility. There are Lake Patrols, particularly during the holidays, but they are not consistent and I would not count on anyone but yourself and/or your group if it came to re-entry, etc.
The trip from the Tavares Lake Eustis access to the dock in Eustis and back is 10-12 miles (depending on exact route). Lake Harris is much larger than Lake Eustis. Again, this is a great place for distance paddling if you're not close to, or don't have the time to drive out to the Atlantic. I enjoy the fact, that though it is technically flatwater, the lakes are different each time depending on the wind, waves, boat traffic, etc. This is also a great location as you can choose to go as far or as short a run as you please.
While this is not a great locale for nature watching it would be an awesome place for paddle fishing. Though I don't fish myself I often find quiet parts of the lake to swim or just lay on the back deck and relax. Difficulty level on this chain really depends on the daily weather conditions, level of boat traffic and how much distance you are willing to take on.
Tavares Access has restrooms and vending machines. I believe the restrooms are locked sundown till sun-up.
I have yet to pay for any of these, but I have never used the Lake Harris Recreational Access. There may be a fee at that location.
Tavares Public Access: Take 441 W through Tavares and access will be on your right just before Leesburg.
Eustis Public Access: Take 19 to Eustis (Bay St) and Access is on lake side behind Gators Restaurant.
Lake Harris Access: 19 S, on right near Groveland