Just bring some ones to tip bell services. We tip $1 per bag when they pick up our luggage on check out day from hotel room 1, and pay $1 per bag again when we call to get our luggage brought to hotel room 2 later that day.
We live split stays and sometimes do 3 hotels. We are staying 15 nights in October and doing 3 at the dolphin, 8 at Poly dvc and 4 tbd. Luggage transfer is super easy, like others said, just call bell services, someone comes maybe 20 min later (or call the night before for a specific time), and they mark all your tags for your new resort and give you a slip. Well, slightly different process from dolphin to Disney owned resorts, but in general this is how it works.
We usually swing by the front desk to check out of hotel 1 and we make sure we have done online check in for both or all stays so our credit cards are linked to our magic bands. We also usually carry a wallet because we use our Disney credit card discount, dvc member card, annual pass discount, and picture IDs often. Any kinks in the transition and we use our credit card until we get to hotel 2 and just swing by the front desk there.
We have annual passes, so no need to have package tickets for us, but as long as you have tickets connected for your 1st leg of the trip that last the length of your stay, no need to worry about getting into the parks between visits.
We also never get a dining plan, so no advice there.
We try to plan our transfer day so that we end up easily getting to our new hotel. For example, when we check out of the dolphin we will do Epcot for a bit, then take the monorail to Poly that night.