Hey.. I know how you feel.. I dont have kids but im a student and I have two jobs... and I too feel exhausted... try some multivitamins. . They could help to keep you energized.... also I have noticed when I eat tons of junky food or simply overeat... I feel heavy and drained of energy... try small portions.. 5 times a day... and what works for me is to just take whatever time I have free and with no excuse drop on the floor and start the workout... don't think too much about it or you will feel lazy... those simple tips have work great for me... and play some good music and follow the rhythm... I have lost 45 pounds so far.. =D
Try your hardest and you will notice the difference in no time =] best of lucks to you.
Keep your goal in mind... read health related stuff(like this forum)... have someone to talk you out of eating... and best of all drink water, walk or have some dry fruits when you do feel like eating (only some /1 or 2)
Also try engaging in a hobby!!
This is what I have tried, seems to help most of the times!!!
What works for me is having a routine. Like going to the gym every monday morning. And every thursday morning for example. This way you will go without even thinking about it