You put all the seeds in one cup? I'm having a hard time grasping what you did (still haven't had my coffee).

If you did indeed put them all in one container, I can tell you what I did for my Beautyberry sprouts (I had about 60+ in one 4" pot). I found a shady spot to sit, dumped the entire contents of the pot into a bowl and gently separated the sprouts. I then put the sprouts into dixie cups (2-3 sprouts per cup) and filled the bottom half with soil and the top half with peat and then added a little water. When all was said and done, I had 20 dixie cups inside a cake box (my wife is a baker and gets these awesome flat-like cake boxes from work... with cakes usually). I have them sitting in my lanai now, so that they're fairly protected from the sun and so far they're doing quite well (it's only been three days). After I'm sure they've take the transplanting successfully, I will thin out each dixie cup to 1 sprout per cup (and might try saving the others in their own cups).

IMPE, lettuce seedlings can withstand a lot of handling, as long as you are gentle. I sow seeds in small flats (mushroom & berry boxes) & use a sharp knife to cut around & gently lift & transplant them when the 2nd set of leaves are approx. 1 inch(or a bit more) long.

I always water them before & afterwards w/ seaweed extract or compost tea, which seems to help.

My experience is like Carol's - lettuce tolerates transplanting and handling pretty well.

If the seedlings are really close together (roots tangled badly) you probably need to do something like Leekle suggested. If there is space between the seedlings, Carol's knife method works great, though I usually use a duller knife or even a plastic plant label as a combination wedge and dibble to get them out.

As long as you don't rip most of the roots off, or leave the roots exposed to air for too long, they'll be fine.

thank you everyone for your suggestions. I will be transplanting them this weekend ever so carefully. thanks again. Glad I found this gardening forum!!