I've found it helpful to talk to the professor/TA and your partners. My TA actually talked to my group for one of the projects I was working on and told them I had some "family issues" and I might be busy a lot and so it kind of helped in the fact that I had back up. I apologized up front to my teammates and they were really understanding in helping work out what I should be assigned for in the group. I find that keeping an open dialogue is the best option. Tell people something is going on (you don't have to specify, just warn them) and that you're going to do your best but it might be a little hectic. Especially if they think it's an issue out of your control they won't be too upset as long as you apologize a lot and try to help out where you can.

Best of luck!