We just did 5 days in the parks with a 5 year old and I skipped the Park Hoppers. I'm glad we didn't do it. I believe it's an extra $52 per person for length of stay.
My 5 YO was exhausted after one park and I can't imagine dragging her to a second one! Are you staying at a DW Resort?
What I did was make most of our ADRs at our Resort restaurants. That way we went to whatever park, stayed until mid afternoon, came back and swam and then went to dinner at the resort. After that we usually opted to not go back to the parks because it was already 8PM.
We had one ADR at MK (first day) so we went to MK, back to swim, back to MK for dinner and rides.
We had one ADR at 1900 Park Fare. We did MK that day. Went to MK, back to swim, went to GF for dinner, stopped at MK afterwards.
When we went to Epcot and DHS, we didn't venture back since by the time we had dinner it was late. DD had no desire to go back either. One night we went swimming after dinner around 8PM.
Are you early risers? If you are you might be heading back for a break earlier in the day and be able to make it back out.
I did find with a 5YO that as the week wore on she was more and more tired and could barely stay awake for 10PM Wishes.
What time do you arrive? Perhaps you can squeeze in some more park time on arrival/departure days. We couldn't based on our flights but if you do this (even for dinner and fireworks at MK) you can get an extra day for $3 a person if you add a day.
ETA: it really also depends on which parks you think you will do most and where you are staying. Travel between parks can eat up a lot of time. We were at BLT but it took a while to get to EPCOT between transfering at TTC and such, another reason why we didn't go back to Epcot in the evening.
This was just my own experience, I hope it helps you a little.