We have been quite a few times, so I can hopefully help.
The time of year will obviously impact - October half term for the Halloween festival is obviously more expensive than say February half-term.
Pricing is difficult because you can cut right back and do it for much less, or go all out and spend a fortune.
We have always stayed in Disney hotels, purely for the convenience and the extra magic hours, but our kids are early risers and are always ready for it! They love the characters in the Disney hotels in the evenings too.
Depending on flight times we make it work that we have three full days in the parks. If we need to we stay either side of our Disney booking in Campanile Val de France, basic hotel but more than adequate and they have lots for the kids.
Meal plans - we have gone with and without and aren't taking it next time, we found that it worked out a lot of money for say breakfast when really we just wanted a coffee and toast. Last time we ended up using meal vouchers in quick service restaurants which defeats the purpose.
Definitely bring snacks, there is a lot to pack in so we found we could manage the onset of hanger if we were queueing.
I bring those little concentrated juice bottles and add a little to water bottles too, my two dont like fizzy drinks so it made plain water a bit more appealing.
We have always booked through Magic Breaks, their customer service has always been spot on for us and it took the pressure off. We book flights and transfer seperately.
3k sounds absolutely doable, ours usually comes in about 2.5k with an offsite additional night, character dining, food, and spending money.
If you have any questions just PM me!