You really are talking about several different types of holidays and you need to work out which you want to do.
If you want it easy and just a relaxed time with your DD it is hard to beat the sequoia out of the options you mention. You are right there in the disney bubble and can walk to the parks. You can go back to the hotel room easily during the day and then return to the parks.
Davy crocket is much cheaper. But you have to drive their and back everytime. I know people who love this option and don't mind the drive at all.
My explorers is a bit if a compromise between the two. You can't walk to it but you can get back to the hotel during the day (like for dinner I remember the dinners and breakfasts being amazing but that was some years back).
For me being able to walk/ roll (DS is a wheelchair user) back to the hotel is really important. If I didn't have that complication I would give serious consideration to my explorers.
You can do disney in 2 days, I've done it in one but you end up with more of a taster. Less than 3 days 2 nights you will miss a lot. We go for a very relaxed 4 nights 5 days. The thing most people don't think about is that if you are onsite and you do extra magic hours, you will miss the queues (empty disney is beautiful) making the day far more pleasant. Hit two extra magic hours and you will have done the bulk of the main park without any queuing at all. However you will be up very early in the morning which makes staying up late for wishes (evening show) challenging. You need the two mornings and a separate evening to make it work easily AND avoid the queues. You can cut down the time by skipping the studios but actually I think some of the best rides are in the studios park like Stitch live and animagique which are quite magical at that age)
That said Ime the kids don't really care how long you spend, a day or a week it will be Fantastic regardless. However unless you are a real disneyphobe a little longer is way more relaxing for the adults.
Now the whole paris from Sequoia thing. It's really easy, the station is on site and the train takes you into the centre of paris. BUT if you are staying on a disney hotel with a disney dining plan and a package for tickets I would give serious consideration to the cost. For us, if you catch it at the right time it is cheaper to do a day trip on the eurostar than it is to stay an extra night in the sequoia and travel in. Especially if they run kids for a quid again during summer holidays. Get about the same length of time in Paris too.
I also found leaving the disney bubble very jarring and enjoyed Paris the less for it made worse by my purse being knicked and actually enjoyed the disney holiday less also.
If I wanted to do both I would stay somewhere like val d'Europe and travel in to both. But personally I'd be very loathed to do both in the same holiday again.