I typically just park my ECV in a nice spot by the curb, with my daughter either standing behind me, or next to me if it's the later parade. (I *LOVE* MSEP!)
Since my PT has been progressing, and I have (finally) reached a point where I can walk and stand longer, on our "quickie trip" at the beginning of January, our daughter would often pilot the ECV for me while I would walk for a bit. Even if it was only for short stretches, it sure felt good to be "tall" again at WDW!
So if you need to stand during the parade, you could perhaps have one of your DDs sitting on the Rollator while you stand during the parade, if that helps. And, if you don't want to use the Rollator at all while watching the parade, you can always just kind of fold it up and the 3 of you stand together in whatever spot you want.
I was really glad for you that your dad had that Rollator to borrow! I know you are concerned about your trip budget, and I'm sure that it was a relief to not have to worry about that!
There are TONS of money-saving tips here at the DISBoards (and on many other Disney-related sites all over the Internet) so suffice it to say that my favorite souvenirs are my happy memories that I bring home from every trip...
I hope you and your beautiful daughters make all the memories you want, and find all the Magic you can on your trip!