Only reason to wean them that early is if your doe is on a tight breeding schedule. I would not do that. Espacially if you plan to put them together again, that's not weaning. I seperate the boys at 12 weeks (10 lbs rabbits), the doelings stay with mom up to 5 months, she weans them when she likes to.
In a pinch, like when there's the next litter coming, kits can be weaned at 4 weeks, I prefer to keep them with the old ones as long as possible for socialising.
What has sexing to do with weaning anyway? At that age it is no problem to seperate them from the doe for some hours, they nurse only twice per day, and at that age the little gremlins can be a PITA to the doe anyway if she doesn't have a chance to get away.
Just keep your daily routine, get them sexed if you can't do it yourself, and put them back.