3 Days in Paris

Can't help, but good luck! 4+-bedroom apartments are very uncommon here, and even then, folks must be happy to share a double/queen bed.
You might have more luck finding two side-by-side apartments in a tourist-oriented residence, but this does mean that the whole group probably won't be able to hang out in one space.

You might want to look at PLUMGUIDE.com

they boast 3 and 4 bedroom apartments-not inexpensive-but a start and gives you and idea. I have not used them in the past, but have heard decent things on this forum and others. Good luck and have a ball!

For apartment(s), try Vrbo.com. Some may want renters staying more than just 3 days, but it’s worth looking. Another possibility is Gites de France https://www.gites-de-france.com/en .

For food tours, as well as cooking classes, Rosa Jackson is fabulous. She divides her time between Paris and Nice, but contact her and see if she’s available during your Paris time - Edible Paris http://edible-paris.com/rosa-jackson/

I’ve debated about offering some extremely unsolicited advice which has nothing to do with your question.

While I’m thrilled you are all traveling together, I want to suggest your group makes an effort to engage with other members of the tour. I’ve done 11 RS tours and on one there was a group of 9 together with another 4 loosely associated with them. It really changed the dynamics of the group as they were not good about mixing with others in the tour group. I’m sure you’ll have fun together and just want to throw it out there that you might mix up seating sometimes and get to know other travelers.

Meanwhile, the Belgium and Holland tour is excellent!

That is going to be extremely expensive and hard to find.

You may do better looking for two or three separate places.

Because this is the size of a tour group, and you are staying only three nights, you would do well with an apparthotel or hotel. Three or four rooms would provide three or four bathrooms.