I find that sharing the load can help a lot, encourage your assistants to contribute towards portfolios and parents too. Ive sent home My Weekend templates where the parents can share what they have done with their child over the weekend, which will be stuck in their books.
Sometimes a picture itself can show a lot, I have simple photos with headings I can... Tidy Up, Hop on one leg, etc in the portfolios as well.
The other day we were showing our children a green frog we found in our playground and one child held it so I snapped a photo and put it in his portfolio with a few lines under it.
I snap photos whenever I see the kids doing anything so I can actually do my obs off these sometimes + I have a good memory so I don't really need to not interact with the children in order to get my obs done etc and I find my 3 hours/week programming time means I can write up my obs and do all my programming & planning for the next week and my assistant uses her 2 hours/week to sort out portfolios and stick everything in so I am not spending 3 hours gluing things in a book!
Anyway yesterday morning one parent wrote in our communication book she looked through her childs portfolio and really was amazed by the various activities we do with the kids and the skills we are teaching them and she just wanted to thank us and she really appreciated the effort we were making....

Made my day, just wish more parents were appreciative, sick of being thought of as a glorified babysitter