If you're okay with split stays and really like BW/BC, adding on there isn't a bad idea at all for Epcot area. I would try a visit to Riviera. Their studios are really nice, and resale Riviera is the same price as BW/BC and gets you a much longer life span. I know, it sucks the points can ONLY be used there, but your family is very young, and you have your Poly points to get 1Bs at BW/BC or other OG14.
We've had good luck with waitlists, and your 250 Poly points should work well for 1B/2B if and when you need it.
The other thing is your kids ARE young. Once they're locked into school schedules and sports/band/whatever, you may not be able to go as frequently as now. Instead of running out of points from frequent trips, you may decide to go baller just on peak weeks due to their school schedules.
We thought we'd be fine pulling them out of school (and we got lots of trips in during Covid/remote learning,) but now in middle school, they can't miss that much time, and so much of what they're doing is in-person lecturing with Chromebook work. It seems like they COULD take their Chromebook on vacation and do work -- and my son did do some of that, but it really can set them back missing the instruction in class that goes along with it.
All that to say, I was all about addonitis until I got a new job that makes it very difficult to get time off and the kids entered middle school with a much more rigorous agenda.
Gone are the elementary school days of macaroni art and every freaking holiday being a themed daily celebration (Dr. Seuss's birthday! Favorite sport/team day! School spirit day! Easter! Christmas! Thanksgiving! St. Patrick's Day! Valentine's Day! Crazy hair day! Funny socks day! *** day! LOL.) Now they're like little programmed Einsteins and expected to be all grown up by 5th grade.
Your 250 Poly +100 whatever you get may hold you nicely for a while. We're at 400 points and DH just asked if we should get another 100 somewhere for booking priority, and I shocked him when I said no, I think we're good for now.