This might sound crazy to you but at that age my LO wanted to go to bed by 6:30pm. She would go to bed, wake about an hour later for her last feed, and I would put her directly back to bed. She then slept until 3 or 4am for her night feed (dream feeding didn't work for us). One key indicator that that was what she needed was she was miserable after 6:30pm no matter what we did. Unfortunately for me that meant wake up time of 6am but I got used to it...
Worth a try? Also, what do you do during activitiy time? My LO was also undertired as someone brought to my attention because she would party a couple times a night - she became much more aware at this age!