We have a family of 6 but husband doesn't ski, so I'm heading to the slopes with 4 kids from 4 up to 9yo. Stressful to say the least, but mainly because of safety issues.
How often do your MIL and niece ski? If they don't, then first go over safety stuff the night before. Also, the night before all my kids get their extra "stuff" like gloves, goggles, and put it in their helmet. IMPORTANT: Have them practice putting on any gear they're not used to and encourage a mom's-hands-off policy the next day! Skis (not boots) get loaded up in the car the night before. The next morning they put on outerwear, swing a loaded helmet over an arm, and head out the door with their boots. We tried wearing boots to the slope, but it wasn't as easy as I thought and then you don't have anything else to wear during lunch breaks, etc., to give your feet a break.
As for the skis, I think I finally hit on something at my slope that will work great. Our ski hut is near the unloading area, so first thing is kids truck their skis to the hut. Then we don't have to worry about theft from the racks and we don't have to carry them around. We head to the lodge and while they're beginning to suit up I park the car. We finish suiting up, and I'm trying to make them as responsible as possible for everything! I check helmets and help the smaller ones with boots, if necessary. My nerves were frazzled before we even left the lodge before because EVERY SINGLE KID used to expect me to suit them up like they were Princess Grace and I was the handmaiden.
Things go much better now! Then we head to get our skis and put them on! Don't know if you have a similar set up.
I think I'm finding out the key is to be sure they know what they're doing before we get to the hills. Last year when we were all novices it was like a Laurel and Hardy skit.
As for the little one, you're either going to have to totally give up your day with your kids or put up the$ for daycare. It's worth it if you want to ski. If $$ is a problem, then there's no way around having to stay with her and help her.
My ski technique sux. I know everybody says my kids will eclipse me one day, but right now I can ski circles around them. We can't separate, so we are held to the slope of our lowest common denominator. I have always skied in front of the kids looking back, the total opposite of what you're supposed to do. But, they knew to head for me and run into me if they started to lose control or get scared, and last year my then 4yo did ski into me a few times while he got used to slope speeds and turning with confidence. I execute a turn and my body immediately turns up hill. This year they go in front of me and it is hard to get used to not facing backwards for everything. Sacrifice I have to make temporarily. I hope to ski by myself soon and teach my body to look DOWN the hill, not UP the hill!
But, again, safety is an issue. The first run of the year we talked about it on the way to the slopes, and on our first run down the green slope we took it slow and talked about things like where trails merge, staying in the middle away from trees, how to fall backwards if you're heading to a tree, etc.
BIG THANKS TO ALL THE DIVAS HERE FOR HELPING ME WITH SAFETY LAST YEAR. Maybe going over that stuff with MIL and niece would be a good idea next time.