increase the hose / pipe diameter between pond and garden. from 1/2" up to 1" (inside diameter). that in itself with reduce pressure loss.
any sump pump, to trash pump will work, but if you are gong to use a trash pump. you need a larger diameter hoses. so crud does not get hung up inside the hoses. and at fittings. most trash pumps can pass X size solid. sump pumps on other hand tend to not handle moss, small fish, little rocks, and mud very well and will clog up quickly.
most sump pumps and trash pumps are not really rated for continuously running. and can and will over heat and spew oil out of them, or end up shocking you as electrical connections come un-done. while the pumps can run for some time. they are not made, to run non stop all day long most of the time. they are better suited for running a few minutes to half hour at a time, and then having an hour to cool off. then run again. (granted that may be extremes for some pumps, but trying to get notion across about utility rated pumps),
to note it 2 to 6K GPH (gallons per hour), seems like way to much pump. your talking a 2" maybe even a 3" pipe feeding them and coming off of them. your going to drown the garden. and i am going to guess the small generator may not even handle the pumps, as far as AMP ratings. i may be wrong. back it down to couple hundred gallons per hour. at say 40 PSI at around 10 to 20 feet of head of water. maybe up to 60 PSI. and you will more likely feel like you have a "garden hose" hooked up to the house water supply.
make sure you pay attention to AMP ratings, of the pumps. so you do not go over your generator max amps for 110v plug.
in order to get trash pump and/or suction hose out far enough into pond, so you are not sucking in weeds, fry/ small fish, and dirt. your going to need some sort of "float" trying to toss suction hose or trash pump onto end of rope and "fling, toss" it out into the pond, (shakes head no) just asking for clogged up pump with mud.
hard board insulation, to pvc pipe, to milk jugs, to old LP 5 gallon or smaller gas tanks, can be used as floats.
keep the end of pump or suction off the mud/ bottom by a couple feet if possible. if not any sort of sprinkler head will get clogged up quickly.
if you want to make a "custom" diy spray bar / sprinkler. take say a 1/2" to 1" pvc pipe, cut a V grove into a 2x4, and then clamp pipe into V notch, then use a drill press, to drill a row of holes, 1 or 2 rows, start with smaller size bit first and see what it like and if need be go with larger holes.
if you are pulling the pump in/out each time used. then some sort of telescoping pole helps. example a manual "pole saw" that reaches 30 to 40 feet up for cutting a branch, just take blade off, and use the pole to push/pull hose end in/out of pond.
if you are going to install hose for good, "block poly" pipe, is what i call it, comes in "rolls" 3 to 4 feet in diameter. most local hardware stores have it outside some place. tends to be cheaper. you could still use as a temporary hose above ground, it will want to coil up and lay ugly, if you leave it out in the sun un-rolled, it should heat up enough in a days time, to lay flatter.
