GDub,

That is going to be a pretty pond!

Is the entire bottom of the main pond going to have a liner? If so, then you will need a very efficient biofilter process since you won't have any plants in the shallows of the main pond.

There are going to be a lot of nutrients for algae unless your really circulate water through your biofilter area. (Do you want algae during the bloom times, or want clear water?)

Can you get your pond running (and mature) and then determine if you need the skimmer? I would create a "place" for the skimmer during the design phase, then add it later if needed.

P.S. It looks like you are going to have some cinder blocks at the deep end of the "gravel beach". These can be "toe-stubbers". I remember someone's good idea to place plastic pots just inside of the rock wall. They then planted water lilies, etc. in the pots. This would give you a little bit of nutrient uptake in the main pond AND you could then tell grandkids not to go past the plants. If you place the pots at the proper depth, you could wade out and "weed" them by hand if any undesirable plants take hold.

Good luck on your project!