The other day I walked into old navy with lola and carmen and a few gift cards and walked out with a whole lotta active wear. Now, I'm not going to get into the benefits of a solid running shoe, or moisture wicking fabric in a shirt BUT if you are needing something on a budget that will perform, old navy has some great pieces. Lola chose the above basics for a great workout outfit. Just be sure you choose "active" leggings and not "yoga" leggings if you will be running. I find they stay up better..
A great way to get your children into a little fitness routine at home with you is to get them their own gear (Of course, using a can of soup works just as well). I lift weights at home and picked up some little two pound hand weights for the girls to use. Obviously you need to use your own discretion as to what your child can and cannot handle and I do not recommend any weightlifting for your kids at all without discussing it with a doctor or trainer first. As for Lola, she does three different arm curls with a repetition of fifteen each, three times a week.
Dig it babies.