Lens best for my needs 50mm, 40mm or 85mm

Sigma 30mm 1.4... My favorite indoor lens...

The Canon 35F2 would be perfect for this. For groups outside, you need to stop down, so you would want apertures smaller than F2.8. For inside shots of an individual, you need F2 for low light. Groups may require smaller apertures indoors, so you may need flash for more than 3 kids. I use the 35 on my crop for kid photos. Toddlers don't keep still for long, so a long lens with very shallow depth of field at late apertures is not so good.
I prefer Canon color to Sigma, but this is subjective. The old Canon 35F2 is a bargain. If you get one, be sure to use the hood. You need it for flare reduction on the old lens, but not the IS version.

Did not like my 50mm on crop. I think 85 would be way too much. 40 or 35 would be pretty good I would think. However on FF, my 50mm is wonderful

On a crop, not having any experience with the 30mm Sig, I would opt for a 28mm or 24mm if I was going do any group photography. Your 50mm will do fine as a portrait lens on the crop body.

I was just going to ask which 35 should I get. I still might get the 85 in a few months for youth indoor basketball. But will get the 35 or 30 now.

I have the Sig 30mm (old version) and it basically hasn't left my camera in 12months of owning the thing.

Great walk around, general use lens!

I have owned the 50mm 1.8 also, and found it certaintly got less use due to the portrature nature of the length on a crop sensor.

Yet to try the 85, but something i'd like to play with.