Another vote for skipping and/or dispensing with curriculum. We never used MEP. We started with Singapore, but we skipped ahead to find the appropriate level of challenge (typically 2B for my kids at KG age) and we skipped around liberally within the program.
My kids actually liked Singapore because there wasn't much repetition and if there was too much it was very easy to sort through the exercises and find the next interesting different thing. The word problems for level 3 or 4 on up were really interesting to them, as there were often multiple ways to tackle them, and they involved multiple steps and the sort of "brain-teaser" questions I recall only getting once I had been taught algebra. I wouldn't say Singapore is a magic bullet. It worked for us because we (a) didn't do the easy first few levels and (b) found it easy to skip around in and glean what the kids liked from it and move at whatever pace was right for them without actually spending a ton of time at it. My 8-year-old is finishing 6B (~7th grade) and has typically spent about 15 minutes on it a few days a week.
We too have enjoyed Challenge Math and Calculus by and for Young People. We also liked Hands-On Equations. The latter is suitable for 5-year-olds and up, so long as they understand basic multiplication and division. The two other ones are probably more suitable for kids 8 and up and have enough stuff in them to challenge kids up to the high school years.
Math isn't nearly as sequential as a lot of curriculums lead you to believe. You don't have to wait until after ratios and fractions to introduce algebra. You don't have to memorize the timestables before learning long division. You don't have to master multiplication before learning about complementary angles in trapezoids. If something important is missing you'll bump up against the gap and you'll know what needs to fill it. "Oops, division of fractions, didn't I ever show you that? Well, here, I'll explain it. Here's the part in the book where there are some exercises, if you want to practice."