Is it advisable to connect a sump pump to pop-up sprinkler heads?
Ingenious, except I’d worry about: 1) timing, 2) seasonal conflict, 3) head contamination, 4) pressure stress. 

1) Timing: Murphy’s Law...but you could locate the heads away from decks, walkways, etc.

2) Seasons: Seems like the sump pump would run most during the “wet” season and not during the “dry” season when the sprinklers need it most. Could you install a valve to allow a regular water source during the dry season? (It will be most difficult during the shoulder seasons.)

3) Head Contamination: I don’t know what the pump is draining, but it would need to be very very clean. Or, you’d need a filtering system...which sounds expensive. 

4) Pressure Stress: You’ll need to “size” the system (number of heads) appropriately to match the size of the pump or it could blow the heads into your neighbor’s yard.