With a litter that size, I would start them on soft food now(I used Purina Pro Plan kitten) 3-4 times a day and then dry I just left out alongside fresh water. At the same time as I introduce solid food, I get them in the litter box. Try to find a box (like something that pop/soda is packaged in) and put litter in. I use Kitten Attract and has worked wonders for me. Take a front paw and show them how to dig with that paw and the rest should be history. Doing this about 10 mins after they eat is good as that's when they will need to go. I had a litter of 8 this past summer and all were trained and on food at 4 weeks...they obviously needed the extra nourishment.
As for letting the kittens go to their new homes is a good question. I let my first litter go at 8-9 weeks and this last litter they were 10 weeks. As long as they are eating solids, drinking water, totally litter trained and close to be totally weaned from mom, then it's ok. I called my vet and that was their advice to me.
Oh do you have any pics?? We love pics of baby kitties around here