Bike routes that mesh with OWS at Lanier or Redtop

Have you considered Lake Chatuge?  The Clay County Recreation center (just over the border into NC) has a nice beach with an island you can swim around and the Beast of the East bike course starts there and is marked on the road.  You can find a cue sheet on the Smokey Mtns Triathlon Club website: http://thebeastoftheeast.net/

I rode this course after the 5k swim race in May and it was lovely.

100% x2 on this!
I did swim/bike here several times this summer while training for IMLP - I would swim straight out to the island, then do laps around and around, then back in - swim capped garmin says out and back with 5 loops around the island is about 4500 yards. Then two loops of the bike course - lets you pick bottles up at the car - and it is easy enough to cut the second loop short. I never had a long run to do afterwards - usually only 15 minutes, but you can run a good bit further out across the dam if you want - it is pretty flat going until you drop down that monster hill on the back side of the dam.

I haven't ridden at Mary Alice Park, but did swim there about once a week - I would swim out to the no wake buoys, swim from buoy to buoy, then back in to the swim area buoys and swim that jiggy-jaggy line (good sighting practice). If I remember correctly that measured right at 700 yards. The last time I was there however one of the no wake buoys had gone missing...

The Reality Bikes route from MAP is a great route.  Once you get through Cumming it is all country roads without a ton of traffic.  I think this ride is just shy of 50 miles but it is easy to add miles. 

I also do a route around the lake, if interested I can either send you the mapmyride link or send you a cue sheet.  This route is almost exactly 50 miles.