Why not make your own? Or does it have to be on a website?
Tactics training for beginners

Currently I make my own, but it could be nice to avoid making and printing them, and having alot of diffrent tactics, instead of the 5-10 positions I give each week.

My coach (rated approx 2200 FIDE), makes us study endgames, especially King & pawn endgames and King, pawn & Rook endgames.
Maybe let 2 of your students play each other in an endgame senario, and then switch sides?

You might look at GameKnot.com - they post two puzzles on the home page each day, one easy & one hard. The easy ones would probably be suitable for your students.
There's a large archive here too of variable difficulty...
http://www.chess.com/forum/category/daily-puzzles?page=1
and more still...
http://www.chess.com/forum/category/more-puzzles
but some of those are quite difficult!
I'm coaching a few children with around 800 rating points. They have yet to get a rating, but they play quite well. Any tactic wepsite which is free and have very easy problems. Mate in 1-2, winning hanging pieces, or other combinations 1-3 moves ahead?