A prep sink would help greatly by giving you multiple work triangles so that many people could work in your kitchen at one time with minimal path crossing. I agree that lengthening the island toward the table could be helpful. If you don't want it full length all the time, then the end of it could be a drop leaf, or a rollaway cart. I encourage you to check out Elizpiz's kitchen. There are links to even more pics through the Finished Kitchen Blog. She has a narrow island with the sink facing the cooktop. In some ways, a narrow island with a sink would be great. It could be accessed from 3 sides! It would be right there for filling and emptying pots. A baking zone could be set up on the oven side of the island, separate from a meal prep zone, which is also separate from the cleanup zone. That's 3 people minimum that could work simultaneously. It's great to hear you've got so much food storage space. Yay! : ) I don't know what to tell you on your burners. If you've got the space and funds, it might be worth it to go bigger. I haven't heard too many people regret going bigger on here but I have heard a few regrets about going smaller. My plan right now is to supplement a 4 burner with some induction burners. Check back in 5 years and see if I made a wise move. Gulp. We don't want to do gas, so we're more limited in what will work well for us. Oh, Elizpiz has a 2 burner domino induction next to her multiburner gas cooktop. Might be the best of both worlds. Here is a link that might be useful: Elizpiz's kitchen on the FKB

Check out Ikea--they have lots of carts and islands. Alternate idea...was at Container Store recently and saw a lot of stacked storage units. An Elfa unit with butcherblock top looks very purposeful and comes in white or stainless-like metal. If you don't need a hefty unit on wheels, you could mount a nice looking top on some other stacking system sold by another vendor. A fabric skirt would cover the entropy if needed. The glory of these kinds of solutions is that they can be removed quickly and can travel with your MIL to another place. (Have moved two different in-laws into and out of sr. housing.)

There is no easy solution. A portable dishwasher would be a drag to use and take out and store - and then the sink is being used to drain the water. An 18" dishwasher is quite small so you undoubtedly have to do multiple loads all the time. I live alone but when I cook a "real" meal I often can't fit everything for prep and cleanup etc. in my full size dishwasher. If there is any money in the budget, I would contact a cabinet maker to see if you can change out the cabinets so that one is 24" for the DW and the sink cabinet is smaller. As others have posted, a smaller single bowl sink with a dishwasher would provide way more functionality than your current double bowl sink. ETA - Honestly if your choice is 18" or portable 24" then I would just opt for hand washing while you save whatever is necessary to modify cabinets for the 24" built in dishwasher. With the 18" you are going to wind up hand washing almost everything anyway. With the portable, the logistics are so terrible that hand washing would be more convenient and you would probably wind up hand washing rather than hauling it out and setting it up a lot of the time. I had my Cuisinart stored in an inconvenient place and I often decided NOT to make something using it because I didn't want to deal with hauling it out and putting it back in.

Agree with Skippack Tile. No cart. No island. Take some time to edit what you have on the kitchen counters. It looks like you have lots of decor items taking up valuable real estate on your counters. In particular all of the items to the left of your sink and on the peninsula can be removed IMO. I would also edit the items to the right of the sink. If you remove part of the decor, you should have plenty of room for actual prep and cooking tasks. IMO most of your kitchen counter items look like items that belong elsewhere in your home and not in the kitchen. While you are editing your decor, take down everything over the cabinets.