I would not remove the tub. Yes that will be a negative to some potential home buyers. Best wishes!

Like pretty much everything else, it depends. In my neighborhood, that would not be a problem and might actually be preferred. Having said that, though, I agree with Susie; ask your realtor or at least look at recent sales in your neighborhood.

H B makes a great point worth repeating: “For bathing little kids -- one does not leave them unattended anyways, so it may not matter if the tub is in the "kids bath" or the master.”

This is (or should be) certainly true. When my nieces and nephews were little and would come for a visit, they took their baths in the giant-to-them master bath’s whirlpool tub—jets full-blast!—despite the fact that each of our upstairs guest rooms has its own full bath with a shower/tub combo. (I’m not sure anyone’s ever taken a bath in either one of them!) And when it comes time to remodel, out they’ll go in favor of more adult-friendly walk-in showers.

I’d remove it . Within reason you can’t let what someone else may or may not prefer when you sell dictate what you’d like to have or what will work best for you now.

What is the problem you are trying to solve? Crowded sink area in the morning?

I don't think you have enough room for a double sink. In terms of your vanity, it looks like what you need more of is storage and counter space. If I were you, I would enlarge the vanity up to the wall, with a single sink the middle, giving you lots more counter and drawer space on either side of the sink.

Toilets are expensive to move -- I don't think swapping the toilet/shower location would improve the functionality of the room, so I would leave it as is. Replacing the tub/shower with a walk in shower would be nice, but I would consider frosted glass if you go the walk in shower route -- I think clear glass could get very dirty looking quick in a bathroom used by that many kids.

I agree with everyone who says your vanity is too small for 2 sinks.

You have not mentioned that you are lacking storage but if you are, this idea could maybe work:

The current space reserved for the toilet seems big. Maybe you could steal a bit of that space and have a wider wall between the toilet and shower and insert a narrow long pull-out to store toileteries. Pull-out can be any width/depth/height. If the shower plumbing is in the way, you can still have a shallow one:

https://www.google.com/search?rlz=1C1CHBF_enCA770CA770&q=pull-out+cabinet+organizer+images&tbm=isch&source=univ&sa=X&ved=2ahUKEwi-lO6ygZTgAhUn8IMKHYm5AOgQsAR6BAgDEAE&biw=1536&bih=724#imgdii=6MrjIgZGDPoAVM:&imgrc=UFK6pQY_l196lM

Do your kids use the bathroom one at a time, or share together? What are their ages and genders? If girls, will they have room for make-up tables in their rooms?

Also, where do the two doors go to, and do you need them both?

What is below this bathroom? Ground floor? Basement (finished or unfinished?), concrete slab, or crawlspace?