Delaware is going to get you 2x, the bridge & near Christiana Mall exit 1 . You will pay for the Bay Bridge south of Baltimore.
You can avoid both tolls in DE, just get your maps out, we have had good luck pulling our old 30ft TT on the secondary roads.
You can avoid the Bay Bridge by going around Baltimore on the west side. It is just a longer drive. You could also go through Baltimore but I would not recommend it.
If you want more details, give me what your planned roads for DE & MD & I'll have my DW look at her directions that we use. I just drive it