Lunges work wonders. There are a variety that you can do:
-forward lunge
-backward lunge
-side lunge with med ball/dumbbell lift
-clock lunges (imagine as if you are standing on the face of a clock and lunge to 12, 2, 3, 4, 6 then do the other leg)
-split jumps/jump lunges
Squats - try a one-legged training approach, use Google images/youtube to get an idea of how to do them:
-Bulgarian split squat (start without weights, then do 'goblet' style, then 'suitcase' style...google Mike Boyle, CSCS out of Boston for more info)
-Single leg squat/sing leg get-up squat
Pelvic tilts will help the hamstrings and the glutes
-Regular pelvic tilts
-Single leg pelvic tilts
-Regular pelvic tilt on step or core ball (can also do these single leg)
-Weighted pelvic tilt (just put a weight plate on your hips)
Tensor band exercise: Kneel on a mat and hook a tensor band around one foot with the handles or ends in front of you. Make sure the band has no slack. Drop to your hands and knees with a flat back. Kick your leg straight out behind you slowly and return to start position.
The grande finale - do a pelvic tilt/roll out with a core ball. Start by lying on the ground with your heels on a core ball and legs straight. Lift your butt off the ground but keep the legs straight. Keeping everything nice and tight (imagine as if you are holding a quarter between your butt cheeks; gross I know but it will help), dig your heels into the core ball while bending your knees and rolling the ball toward you. Pause a moment and return to start position.
Good job on losing the baby weight and keep up the great cardio routine. However, do also understand that genetics also play a role in the overall shape and appearance of your muscles, so while you might be able to tighten your glutes you may not be able to get that nice round booty bump if you're not genetically blessed.
Feel free to PM me for more suggestions!