If you don’t want to do All The Notebooking yourself, then I would recommend to:
a. use an online Google Doc for the notebook and then when stuff opens up again then transfer it into a physical notebook
b. have everyone do CAD designs! and take snips of them and put them onto the doc. These images can be printed out later and pasted into the physical Engineering Notebook when the time comes.
c. for sketches, have the team do individual notebooks (it is sooooo helpful) and have them draw their sketches in there along with anything else you want them to write down for the Engineering Notebook. When it is time, you can cut and paste the sketches into the notebook.
d. when the time comes to write in the notebook, divide the work between everyone so you don’t have to do it all yourself.
If you’ve already started a paper notebook, I would recommend to keep using it and paste in any printed images you would have had to print anyway. For sketches, I would recommend to have the team scan them (apps like Notebloc or Scanbot are really good for this) and send them to you to print and paste in. If there are any really important sketches that need to be sketched and not printed, you can have the team hold onto them and leave space in the physical notebook for that.
And no, there wouldn’t be any problem with gluing in the paper sketches that you drew today later in the year. However, there might be a slight issue with estimating the space needed, because you may underestimate the space, which would lead to you not being able to insert the sketch, or overestimate the space, which would lead you to a whole bunch of empty space in the notebook.
I hope this helped!