Another vote for just having to change your expectations. That's the Mama life.
I had 2 demanding HN babies, but my third is SO easy. I actually CAN get stuff done, and I couldn't make her nurse every hour or more (like my first two did for their first 18 months) if I wanted to. She's just so calm and laid back and content. I am in awe. I used to think when people's babies sat happily in bouncy seats it was because they had to CIO to "train" them to sit nicely in there. I know now that some babies actually LIKE them. Go figure...
ANYWAY...I like to cook, sew, scrapbook, read, run, etc, too...here are my tips for workign things in...
1.) Put the kids in the bathtub (you may have to wait a bit for your 5mo to be ready for this...does he like a tub seat?) to play. Sit on the toliet and watch the kids and knit for 15 min or so.
2.) Find a safe place to leave out your scrapbooking stuff all the time, and organize your embellishments to be quick to access. I throw some pictures out and glance at it as I walk by caring for the kids. I get a vision in my head for what I want to do, and I might even sketch the idea on a scrap piece of paper. When I get a minute, I can easily crop a picture or two, or make a ribbon flower or whatever. I just content myself to do a little at a time. Since so much of doing any project is getting it all out and putting it all up, figuring out a way to leave it out is key.
3.) For a while, I was sewing for 15 minutes every morning. Slow going, but I was turning stuff out a little at a time. I'm going to start this again soon.
4.) For cooking...devote a Saturday a month to putting everything possible in the freezer or prep baggies. Make homemade mixes, cook chickens, freeze cookie dough, etc so that way you can have homecooked meals in processed food time. It works wonders. If you can't dedicate a Saturday, just get in the habit of having something going all the time...you can play with your kids while a chicken boils. But...cook 2 or 3 at once. It doesn't take that much more time to pick the meat off 3 as it does 1, and you'll save yourself the time and mess later.
5.) Make a list of all the things you'd like to do. Divide it out into 15 minute segments o work. It will seem over-whelming at how long it will take to get anything done at first. Next, make a list of all the things you HAVE to do, and how much time they take. Work on becoming more effecient at those, and find the 10 to 15 minute periods you have to come and go from your hobbies. Again, leaving your things out and ready for the next step will allow you to truly work for that time instead of having to figue out where you are in your project. For scrapbooking, you can try those plastic boxes that let you make a kit. Get 2...one for the paper and picture, the other for your basic supplies and whatever embellishments you select for your current page. Then everything is right there, but can still be shut and slid on a shelf to clean up. Seeing where you have time to do things helps, but also being able to check off a box beside all the things that you do (have to do and want to do) will help you to feel like you aren't wasting time. Someone once told me to make a list of all the things I'd already done in the morning when i was making my list for the day. It really does make me feel better to see what I did with my day.
6.) Organize, organize, organize. The more organized you are, the more efficent you can be and the more time you'll have.
7.) Relax...it's only a few short years your children are small. Hug babies, read stories...it doesn't last long.