If an apartment right next to the Spanish Steps would suit you, so that you can come and go as you please then this looks lovely!
www.apartments-in-rome.eu/apartment_rome/405_1/&zon=10
If you like something more modern then this looks lovely and is also very central.
www.apartments-in-rome.eu/apartment_rome/645_1/&zon=10
I would imagine that your DH might tire easily so a nice central apartment or hotel might be the best option?