I totally feel that panic. When I first got my SL2, my bank account was crying too, so I know exactly how it feels to want a safe and reliable choice without breaking the bank. Honestly, I went with the Panasonic Lumix S 50mm f/1.8 and I have been super happy with how it performs. It is basically the safest bet when you are worried about spending your last bit of cash for the month. Here is why I think you should go with the 50mm over the Sigma for now:

• Weight is a huge deal. The SL2 is already a tank, and adding the Sigma 24-70mm f/2.8 DG DN Art for L-Mount makes it feel like you are carrying a literal brick around. For a family shoot where you are moving around kids, the lighter setup works way better for your wrists.
• Consistency and simplicity. The Panasonic primes are designed to be easy to swap, and they handle beautifully. I have no complaints about the build quality even if it is mostly high-quality plastic.
• Image quality is actually incredible. I was worried it would feel cheap compared to the Leica body, but it is surprisingly sharp and the colors are really natural.
• It just feels reliable. Since it is a native L-mount lens from a partner brand, the autofocus is snappy and I have not had a single issue with it during shoots. Ngl, the Sigma is versatile, but if you are stressed about money and physical comfort, the Panasonic is the way to go. It just works well without the bulk. You wont regret having a light 50mm in your bag...

Late to the party but I had a similar panic when I first picked up my SL2. I tried the big zoom and my wrist honestly hated me after an hour. Since you have that family shoot coming up, you really need something that wont weigh you down while you are chasing kids or repositioning. I eventually settled on the Sigma 28-70mm f2.8 DG DN Contemporary and it was a total game changer for my budget. Here is the deal:

• Portability: Its significantly lighter than the Art series, making the SL2 feel way more balanced.
• Performance: Unless you are pixel peeping at 400 percent, the sharpness is plenty for family portraits.
• Versatility: You get that f2.8 for some decent background blur but keep the zoom range you wanted. Another sleeper hit is the Sigma 35mm f2 DG DN Contemporary. It is built like a tank but tiny. Tbh, 35mm is often easier for group shots than a 50mm if you are in a tight space. Just my two cents based on what actually saved my back during long sessions.

Jumping in here because I was in the exact same spot about six months back. Like someone mentioned, the weight is a huge factor. Honestly, the Sigma 24-70mm f/2.8 DG DN Art is a absolute beast of a lens, but on the SL2, it starts feeling really front-heavy after an hour or two. My wrist was actually killing me during a lifestyle session last year. I ended up swapping it for the Sigma 28-70mm f/2.8 DG DN Contemporary and havent looked back once. It usually retails for around $799, which fits your budget perfectly. Ngl, the build isn't Leica tank level since its mostly high-quality plastic, but it's sturdy enough for professional work. For family shoots, having that zoom range is a lifesaver when kids are running around and you dont have time to swap primes. The autofocus is snappy on my SL2 too, no complaints there. Tbh, if you're worried about bulk, the Contemporary is the way to go over the Art. You lose a little bit of wide-angle at 24mm, but your back will thank you. I've also been really satisfied with the Sigma 35mm f/2 DG DN Contemporary. I use it for street stuff mostly, but for families, it gives that classic look and the all-metal build is gorgeous. It actually looks like it belongs on a Leica body. Since you're on a tight deadline for this family shoot, just grab the 28-70 zoom and youll be totally set for anything they throw at you.

To add to the point above: I went through this exact same panic when I first moved over to this system. I had a family session booked just a week after I spent way too much on the camera, and I was genuinely worried about showing up with gear I couldnt handle. I ended up going with a 35mm instead of a zoom because I was terrified of the weight and just wanted something that wouldnt fail me. I picked up the Panasonic Lumix S 35mm f1.8 and it really changed how I felt about the whole situation. It was so light that I didnt even think about the camera after the first ten minutes, which let me actually focus on the kids I was supposed to be photographing. For me, that reliability and the lack of physical strain was worth more than the versatility of a zoom. I learned that if I am comfortable with what is in my hand, the shots just turn out better because I am not fighting the gear. It worked out fine in the end, but man, that initial stress is real.

Facts.