My 2 cents...
I would not have turn around islands if your lake is long enough to drop on each end.( ~2000' ) The islands I've been around are a pain to maintain.
Room for a jump is a good one. More surface area = more gallons evaporated away each day. So if you have to use a pump, the jump are is going to increase the amount of water needed to maintain level.
As far as planning on a pump and no other water supply, do some math and get first hand advice from someone besides me. But, I'm think this is how the math works:
1 acre-ft = 325,851 gallons. That is 27,154 gallons per inch for each acre of surface area. That is 6,788 gallons per quarter inch for each acre of surface area. If your lake is 12 acres, you would have about 81,463 gallons in each quarter inch. We evaporate 1/4" per day in the summer here in east Texas. So, if we want to pump for 8 hours a day we need at least a 170 gpm pump or about a 60 gpm if we want to pump around the clock. You should be able to get evaporation rates for your area.
Plan your parking boat ramp area. This seems like a small thing, but I've seen some that were not well thought out.
Good luck. I walked an 80 acre tract of land yesterday looking at a potential site. Just dreaming...