I spent some time looking into this because the T7 is such a tricky beast with that weird hot shoe. Honestly, if you want something that actually works without a massive headache, the Godox TT685II-C Flash for Canon is the way to go. It is usually priced right around $120 or $130 which fits your budget almost perfectly. The big plus here is that Godox updated their tech to make sure it works with the missing center pin on your Rebel. Since youre doing a birthday party, you definitely want a flash with E-TTL. Basically, the camera and flash talk to each other to figure out the exposure so you dont have to mess with manual settings while kids are running around. Just point the flash head up at a white ceiling and the light bounces down for a much softer, natural look. It stops that deer in headlights vibe you get from the built-in pop-up flash. One thing to keep in mind is that this model uses four AA batteries. It can eat through them pretty fast if you are taking hundreds of photos, so maybe grab some Panasonic Eneloop Rechargeable AA Batteries when you can. They hold a charge way better than standard disposables. Its a solid, professional-feeling setup that isnt going to break the bank or require a degree in lighting to operate. Just make sure the firmware is current and you should be good to go.

Ive been shooting with Rebels for a long time and yeah, that hot shoe situation on the T7 is a total headache. I remember buying a cheap generic flash for a friends wedding a few years back only to find out Canon removed the center sync pin on the T7 and T100 models... basically broke compatibility with almost everything cheap. Tbh its super annoying but you can still get great shots if you pick the right gear. Since youre on a budget but need something that actually communicates with your camera, I highly recommend the Godox TT685II-C TTL Flash for Canon. It usually sits around $130 which is a tiny bit over your budget, but its specifically built to handle that missing pin issue with its firmware. Its basically the gold standard for budget flashes because it grows with you. Here is what I learned about shooting kids parties indoors over the years:

• Point the flash head at the ceiling, not at the kids. This is called bouncing and it makes the light soft instead of that deer in headlights look.
• Use TTL mode. It stands for through the lens and basically lets the camera do the math for you so you dont have to manual guess the power.
• If you cant swing the Godox price, look for a used Canon Speedlite EL-100. Its tiny, very beginner friendly, and is guaranteed to work since its a Canon brand. I once tried to save money with a manual flash at a birthday and missed the cake cutting because I was busy adjusting settings... wont make that mistake again. Just get something with TTL and bounce the light.

^ This. Also, that missing pin was such a petty move by Canon... it really limits your choices unfortunately. I had issues with a bunch of my older gear not firing at all when I first tried out a T7. It was so frustrating realizing my reliable stuff was basically useless on that body. Since you are trying to stay under $120, you should probably skip the official Canon stuff and look at Godox. They actually bothered to update their tech to fix Canons mess.

• Godox TT685II-C Flash for Canon : This one is super powerful and great for bouncing light off high ceilings. Its a bit bulky tho.
• Godox TT350C Mini Flash for Canon : This is way more portable. Its not as powerful as the 685, but for a kids birthday party, you probably dont want a huge heavy setup anyway. Ngl, the TT350C is likely your best bet for keeping things simple and light. Just make sure you get the Canon version specifically!