Sneak out before the hubby leaves for work (4-4:30am).
Used the trailer when he was younger....tried to make the rides end with something fun for the kiddo. Alternate short and long rides, making sure he's stocked with treats, drinks, pillow, toys.
Now using a tandem. He's 4. Started out with short rides to the park. All rides end with a treat of some sort...playground, ice cream, whatever. He now does up to 50 on road and 27 on dirt. It's now much easier to ride on road and in group rides, though bike and kid total 80# so I'm not as fast as a single bike. It is faster than the trailer.
Sneak out after kid is in bed/hubby home.
Also hike with backpack for alternate excercise, and walk or ride for groceries/errands/library/parents as teachers classes/etc. (I'm a stay-at-home mom)
My sister is a single mom too, working, going to school, raising with her kid, whose father takes her part of every other weekend. She doesn't find much, but finds time to squeeze in excercise too. She amazes me.
It's a compromise but he's worth it.
I used to have an open mind but my brains kept falling out.