The tall grass: roll the stem between your fingers to see if it feels triangular. If it is, then it is nutsedge and you will be successful in killing it. If it isn't nutsedge, sledge hammer will not kill it.
Grub-Ex: you won't kill the grubs for at least 30 days. That product is a preventative product meant to be used before the grubs/moles are doing damage. The fastest acting grub product is 24 Hour Grub Control, or something like that. It will do a good job on the current grubs, but it won't last past a few days, so the new grubs that hatch after that will not be killed.
Gonna win 'em all!