I'm in the same boat here, it's dropped down to about 37 degrees 3 days ago and my 4 pants did fine.
Use the bed sheet for sure, if you don't want it weighing down the plants just put a few things around the plants to prop the sheet up. I use my patio chairs which are pretty tall.
If you can shove long "stakes" into the ground around them then even better. I'm on concrete so it's not an option for me.
Check the weather daily! If you know 35 or less is coming and you can bring em in fir the night then certainly do that. If you use mulch to protect the dirt DO NOT water over the mulch, pull it back so you can water straight into the soil. Wood will affect your soil and plants.
Anyway, good luck with getting those ladies to ripen!