I don't think you use two sets of quote marks, Mr. B, as so:
bind kp_downarrow "sv_cheats 1"
Or, for example:
bind kp_downarrow "sv_cheats 1;noclip"
Which would execute those two consecutively. There's a "wait" command, too, which, suprise, waits for a moment before proceeding. The wait length is pretty short though, so you'll need several for anything useful.