Want stuff for kids for ages 12/9/4. Looking at an October trip. All inclusive probably 4 to 5 nights. Under $5k (not including airfare in that- we will use points).

Finest Playa Mujeres is great! Just recently stayed at Family Selection Grand Palladium Costa Mujeres and it was comparable to Finest. Price point is around what you listed, maybe slightly less for both.

Hotel Xcarat was amazing - we went about a month ago. I believe it was about $7k for 5 nights though. Very nice and very family friendly.

So many great options!

Since you have a family of 5 that might limit you for certain resorts and room categories but most do a good job accommodating larger families.

These are the top ones that my clients love:
Dreams Playa Mujeres - honestly any Dreams resort but this one is top of list.
Hard Rock Riviera Maya
Hotel Xcaret - will be more expensive and rooms may not accommodate 5 persons but all adventure parks are included and offer free transportation.
Hyatt Ziva Riviera
Royalton Splash - new resort but looks like the kid activities are going to be top notch. Food at Royalton's are historically just okay.

Feel free to reach out if you need help planning or booking!

I agree with Breeze's list too.

Dreams PM - always a solid option for families.
Hard Rock RM - beach is coved off but good for smaller children as no waves.
Hyatt Ziva (Cancun hotel zone)
Xcaret is likely not in the price point, but amazing if it is. So much to do.
Planet Hollywood - gets some complaints, but overall a solid option although the water park is more geared towards younger kiddos (we did go when our kid was 11).
Moon Palace the Grand - LOVE this resort but the beach water is brown/murky. But amazing kids club, water park, love the food. Video/arcade lounge. There is so much to do we didn't even care to go to the beach.
Grand Fiesta Americana Coral