We definitely try to start our quiet activities after dinner. We try not to do tv or comupters and such...we'll play a board game, read, color, play cards. Things that help the girls wind down.
Depending on what time she gets up 6 might be too earlly for sleep, but to begin a bedtime routine or quieter activities, probably not too early.
For reference, my 5 year old (and of course they are all different, so take this with a grain of salt) goes up to bath/brush teeth, etc around 6:30. After that, potty, read books, etc, it is usually lights OFF around 7:45, we have our chats and she is usually sleeping a little after 8. She gets up in the morning around 6:30-7.
Best of luck finding something that helps. I do find that with school in, DD is pooped earlier!