man, i totally get the gpu struggle. been there... watching your hardware crawl while trying to render a single frame is just painful. since you are looking for something cheap and easy for the birthday party, honestly, i have been super satisfied with Leonardo.ai Artisan Plan 8,500 Tokens/Mo or even just their free daily tier. i have been using it for a few months for my side projects and it works well without needing a phd in prompt engineering. they give you about 150 credits every single day for free. since you only need 100 images total, you could literally do the whole project for zero dollars if you space it out over a few days. the interface is way cleaner than automatic1111... just toggle a few buttons and you are good. no complaints about the output quality either. heres why i think it fits your needs:

• the image guidance tools are basically magic for cartoon styles.
• you dont have to worry about negative prompts as much because their presets handle the heavy lifting.
• the canvas editor lets you fix small mistakes without rerendering the whole thing. if you want something even more point and click for the actual posters, Canva Pro Monthly Individual Subscription now has magic media built in. it uses dall-e tech under the hood and its incredibly simple for making invites since you can just drop the ai art directly into a template. i use it for family stuff all the time. definitely worth a look if you want to stay under that 10 buck budget.

To add to the point above: you absolutely have to check these out! I love how consistent and safe they are for quick projects.

• Ideogram AI Basic Plan 400 Images Per Month is roughly 7 bucks and it is amazing for putting text on posters.
• Microsoft Designer DALL-E 3 Free Web App is totally free and incredibly simple for cartoon styles. Seriously, they are fantastic and wont cost you much at all!

Just wanted to say thanks for everyone chiming in. Super helpful discussion.