It's been a few years, but when my son was young and kind of clingy and I wanted to exercise, I would pop in a tape of The Wiggles and we would dance along together to the songs. Quite a few times it ended up as me doing the dancing while holding him, but I thought of it as weight training. I had incredibly strong arms back then.
The Wiggles always had these goofy choreographed dance routines that went with the songs (especially in their earlier less sophisticated videos). It was kind of like goofy aerobics. lol. Wiggles videos aren't as common anymore, but sometimes I see them in the bargain bins. I haven't checked, but maybe they can be found on Netflix. It probably won't give you buns of steel, but it will keep you moving and you might even look forward to it.
If you have a Wii, I also noticed that they have a Just Dance Kids game that might work even better. I might consider this one for myself. I really need to move more, my daughter (5) loves the Wii, she loves to dance, and I don't mind dancing to kid songs. It seems like a good fit. lol.
I understand the feeling of just not wanting to cook. I remind myself at those times that the important part is to have a meal even if it isn't ideal. In my ideal world I would have the time and energy and money to cook everything from scratch using fresh ingredients, but it doesn't happen that way. Plus, I have found when I am most consistent with No-S I tend to run into apathetic spells where I lose all inspiration when it comes to meal planning or wanting to put much effort into meals. It can really be a challenge.
But, even when you don't like to cook, one tends to still eat. Put what you've been eating on a plate and call it a meal. It's a start. Unfortunately, I have found from experience that a meal of snack food usually doesn't hold you to the next meal very well (or fit all that well on a plate. lol). I have tried cooking bulk meals in advance and it doesn't work well for me, but having some quick, easy recipes that were scaled down to avoid leftovers did. When I found myself alone with two young kids that didn't eat much (my husband was deployed for nearly 2 years), I found some Dinner for Two cookbooks that had simple recipes in them that I could also feed my children (which included my 3yo daughter at the time). I liked eating freshly prepared food and not having to deal with a lot of waste or left-overs. Also during that time, I tried not to beat myself up for resorting to convenience foods - frozen, canned, boxed entrees, etc. My meals weren't perfect, but they were meals and it all went toward really cementing the habit of having a sit down meal at dinner with my family - and forming the habits of having set mealtimes is very No-S. (and I did manage to follow No-S and lose a pants size during the later part of this time.)
Recently, I found myself in a similar boat (dinner alone with the kids more nights than not) and was also in one of my really apathetic non-cooking modes. The budget was tight, I was tired, overwhelmed, and I dreaded dinnertime. I had started snacking non-stop. I decided to make a set schedule for what I would make each night. The meals had to be super easy, fast, kid-friendly, budget- friendly, and flexible so that I could add some variety to them if needed. So now we have pasta on Monday, soup and sandwich on Tuesday, Breakfast for dinner on Wednesday, hamburger casserole on Thursday, and pizza on Friday. It really helped me get the meals on the table and the kids actually really like it. Plus it makes grocery shopping so much easier. Sometimes when I am in a cooking mode, I go all out and do something special. But, I have back up convenience options for most nights (canned soup, frozen pizzas, Bisquick, canned spaghetti sauce, etc.). Plus, most of these meals are easily adjusted to larger portions when my husband actually makes it home for dinner with us.
Anyway, those are a few things I figured out when I was in a similar situation. I hope you can figure out a good solution that works for you. I totally understand your frustration right now.