I really agree with Plu's comments up above - it doesn't seem right that you'd be the only one giving up something that you really want. It would be good for your girls to see you getting something that means a lot to you, since you are modeling what being a mom is all about. It shouldn't be about self-sacrifice all of the time, but rather about compromises.

Last suggestion, I promise. Would it be possible to train 2 nights a week instead of 3? Or maybe even alternate 2 nights one week, 1 night the next? It might slow down your advancement but might result in a bit more balance between everything. Maybe you can make dessert a family affair on those nights you all can't have dinner together?