I'd missed that you were proposing 10 days. I have some "pro and con" thoughts about that length, and then I can recount some of our experiences.
- Yes, that's a very generous, maybe too generous amount of time. Con: you can definitely do WDW in less.
- On the other hand, PRO: having more time takes some pressure off of individual days. You can spend just a few hours in parks per day and still "do everything." You don't need to feel that a time-out or a ride being down is a missed opportunity.
- But then, CON, if cost starts becoming an option, trimming days is the easiest way to manage it. Because the overall budget is tickets plus lodging plus food. PRO, tickets get cheaper and cheaper per day as your stay gets longer. But CON lodging doesn't so much, and food sure doesn't!
- If you already take vacations of this length as a family then you know your own dynamic, so YMMV. But CON no matter where you are, 10 days might be long enough in one place that any destination gets a bit old. My extended family goes to the beach for a week every year, and it follows a certain cadence. The first days are "OMG I missed you how have you been this is so fun beach beach beach!" Day 2 or 3, everybody's gotten sunburned and run out of energy and is lying around. And then around days 5/6, people are really starting to get on each other's nerves and offend each other, so the trip ends just in time to avoid any seriously hurt feelings. Now, if you were planning to pad the trip with Universal, Sea World, Legoland, etc., then you might never run out of things to do, but even at WDW people might get... dare I say it... bored.
Our first visit was 6 days (minus travel), without park hoppers. We did one day for each of the four parks, plus re-visits to AK and MK. That length let us do
almost everything—there were still one or two rides we just didn't see a good wait time for—and take some "timeouts." We had sit-down dinners every day, including padding an AK day with a lengthy Jiko dinner. We spent an afternoon in the pool. We still went pretty hard; I could see expanding that trip to 7 or 8 days to put more breathing room in it. But if you spend some time splitting up, with the enthusiasts going into the park and the chillaxers staying by the pool, you might be able to accomodate everyone in a shorter stay.
Another topic: dates of visit. BEWAAAAARE of Presidents' Day! Less so next year. This year it's a big deal because Mardi Gras falls on the same week, as well as a marathon and some other stuff. See
https://www.disneytouristblog.com/crowd-predictions-presidents-day-mardi-gras-disney-world/. But note that article also says last year's Presidents' Day was surprisingly high.
February
outside of President's Day is generally a nice low time. So is January, outside of New Years and MLK. I don't know if you're planning around a school holiday, but I encourage you to consider MLK. For our schools, Presidents' Day is only one day off, but MLK was two. We went just a few weeks ago for MLK week and I think we made the right choice. Crowds were higher I'm sure than in the other weeks of January, but much lower than what I saw in the first visit, which was Spring Break. And there was more drop-off in the Tue and Wed following the actual holiday.
Finally, one more suggestion: Do
you enjoy all this planning? Me, I eat it up. A big part of the enjoyment of the trip for me is vicariously experiencing it in advance. But it's not for all (and it's
hard these days!). You might consider engaging an approved Disney planner or
travel agent. They don't add anything to your cost. And the fact is, you
can't do WDW "unplanned"; the kindest thing us planner-types can do for the unplanner-types is either take the burden of plans off them, or better yet, make as many
flexible plans as possible; when somebody says "We're bored, what can we do," have the knowledge to say "Well, park A closes in an hour so don't go there, but we have Extended Entry at park B. There's a show over here, and an activity over there." Maybe don't
pay for anything you don't have to in advance, like ILL$; you can make that decision during your stay. You will have to reserve (and in some cases pay for) things that are "must-dos" for one person or other, like Cinderella's Royal Table. But you can still leave a lot not-set-in-stone.