If you can only get in 30 minutes of work out, it's better than nothing! I say just try your best with the time thing! How old is your baby? Can you put her / him in a jumper for the last half of the workout or a vibrating chair or anything? As for walks, a body in motion stays in motion so doing anything active is great as it will help you keep moving and burn more calories. Also I'm sure your baby would love to get out for some fresh air and it will help instill a healthy life style in him / her from a young age!

Also, from your picture, your hips aren't huge! I have a very hour glass shape and also can't lose much off my hips. I have a big hip structure and a lot of it's bone, so you don't want to lose that! A lot of things can help work your bum area, but if you work it too much, it can actually get bigger as you grow the muscle so it's a fine balance! Do you need help with what type of exercises work your booty area?