We own and use a ridiculous number of math programs, and I have to say that the hardest part is getting organized!
If you are constantly jumping back and forth from program to program without a true set of guidelines, I think it would be very easy to confuse a child, burn ourself out, and possibly miss out on important points or aspects. Of course, this probably depends a lot upon the child in question and the focus of the parent, but I can tell you what we have done and what seems to work well for us.
Alex has always really seemed to enjoy anything math related, quite possibly due in part to our emphasis on it. Regardless of anything else we opt to work on, reading/language and math are the biggest focal points in this house, with science simply along for the ride daily as it just lends itself to being taught efficiently through every activity, exercise, book, etc. 
The very first thing we did officially, although we started ‘math’ almost from the day Alex was born, was to
adopt a ‘Marshmallow Math’ style approach. However, I never did it topic by topic, but read through in its entirety and adopted as many ideas concurrently, in addition to my own. This was the impetus for adopting several various programs, and portions of programs into our math activities.
We started with Jones Geniuses Math Matrix, as this was very easy for a tiny tot to work with. But I constantly had to find more and more math games, activities, challenges to implement during play, because she begged for it and, of course, a toddler’s attention span required VERY short bursts in incredible frequency!
So…now, as Alex fast approaches her third birthday, she is ready for more structure.
The one thing I think is absolute most important: PICK A SPINE to follow, and set aside time every day for it…it doesn’t have to be a huge amount of time…the idea is that you are teaching them that math is an everyday activity, important, and worthy of your time and theirs! If you tend to just slot it in when and if there is time, in a haphazard fashion, I think this sends them the message that it isn’t as important as other things…don’t get me wrong, we still ‘play’ math all day long, incorporating into driving time, board games, songs, her jumping on trampoline, etc., but a structured time is expected, and she looks forward to it.
We have been using RS as our Spine, but we also do bits of Singapore (much better at concepts such as weight, length, number bonds, and more), working on ‘equations’, c-rods and Miquon for a ‘lab’ approach, Jones Genius Math 3 for its memory work and peg system, Life of Fred, Adventures of Penrose, for fun. We occasionally still jump on iXL for a treat, she has almost mastered her multiplication tables via multiplication.com materials, and we sometimes pick and choose an approach from other sources. She loves Peter Weatherall Math now, but that is a ‘treat’ she earns:)
How do I fit it I ? I read ahead by about a week in RS, then go through the other materials to pick and choose their approaches to the same topics, and try to incorporate them into either play or activities leading up to the RS lesson…when the actual RS lesson comes, I often find that it is a bit of a non-event! She is oftenso well-prepared by our ‘hard preparation work’ prior, that the RS lesson becomes just fine-tuning and reinforcement. This also ensures that our sit-down lessons have very little stress and mutual frustration.
I also LOVE that we read a huge number of math literature books as she gets reading practice with a good helping of math. These are some of her favorites, and there are SO many to choose from!
I also REALLY benefitted brom the Kitchen Table Math books…but again, I read through the entire first one and began implementing ideas concurrently, rather than a truly linear approach. It is SO much easier to do the prep work day to day…for example, temperature…every time we go out, from the time she was small, we told her the temperature. We gave her relative temperatures, like a pleasant day, a coat day, swimming outside days, how hot the oven, a bath, the refrigerator, etc are…now, she can tell you approximately what temperature it is in both degrees Fahrenheit and Celsius it is just by experience. Showing her how to do it on a thermometer was a breeze.
It does get to the point where she thinks of ‘math’ as her lesson at the table (usually 15-20 min), and the rest is just fun and games throughout the day!
Oh! And there is a great McGraw Hill app called Tric-Trac that masters addition (it is fun and addicting, strategic as well!) that is her reward of choice!
My daughter is currently using only one math program beestar. It’s helpful. There are two worksheets per week, so I help DD review school work everyday and DD does the practices at weekend. I am still looking for the ordinary one…