Evening energy suggestions ?

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I get up every day around about 05:40 and cycle 6 miles to work. I work all day in an office (IT) and then cycle 6+ miles uphill (I sometimes take a wider route to give myself more of a workout. When I get home around 5pm I grab a shower, get changed and spend time with my little boy who is autistic whilst the wife and mother in law cook dinner. As Alex is autistic he doesn't go to bed until 9pm even though he's only 4 (5 next month) as if we tried to put him to bed earlier he would wake up at 2am and then be awake for a couple of hours in the middle of the night, meaning we'd have to be up with him. By the time I've tidied downstairs its 9:30 to 10pm.

I really want to do a quick half hour home work out, that's not to noisy, but Im knackered and just want to collapse on the sofa. Any suggestions on ways to have a bit more energy to work out in the evening before bed (usually around midnight) ???