Planning my first pond -- a few quetions for the experts here

I think I have a sutable, but mostly shaded, area
near the house for a 1000 gallon pond with a two foot waterfall.
I've resigned myself to battling with tree debris -- falling twigs,
leaves, and seeds -- in the spring and fall. I'm not a big koi fan
which is probably a good thing considering the number of raccoons,
snakes, herons, etc. in the area. However, I'm hoping for frogs
and with a large stream about a hundred yards away and a beaver
pond on the other side teeming with frogs (the sound is almost
deafening this time of year), I'm assuming that won't be a problem.
Plus I'm sure it won't be long before my kids start putting crayfish
and other 'wild critters' in there.

I was leaning towards the Tsurumi OMU-2 pump (3000 GPH max) and
a Savio Compact Skimmerfilter and a Savio Livingponds waterfall
filter. Is that too much pump for a 1000 gallon pond and fairly
low waterfall?

** That pump volume should be OK - just check to make sure your "weir"
will supply a 3000 gph pump - a 6" one is good for ~ 1800 gph - you will
need the 8" one , but don't forget to ask, if you haven't already

What about a gravel bottom in a shaded pond? I've
heard both pros and cons, but I'm hoping that it will add a layer
of protection in case our 70 pound dog decides to wade in one day.

** Yeah - that has been debated here often - I personally don't like them as
I like to "scoop" the bottom with a net when I get a lot of leaves etc. that
have sunk (I don't net my pond anymore as I skim the suface as they fall
and/or blow in as I'm now retired)

Also, is a center drain a must? My gut tells me to plumb one in
in any case. Any comments and advice would be appreciated.

** I don't have one, but my pond is 10 yrs old (before they thought of it,
and don't know if I would do it anyway - hate the thought of cutting the
liner) - but if you think it is a "maybe" - now is the time
Gale :~)