Have you looked at the schemes of learning from the White Rose Maths Hub? I really, really, really like them and they are free. I've got mixed age plans from them as well - don't seem to be in their dropbox but I picked them up somewhere on line.
Your first (and biggest) decision is whether as a school you are going to go for a mastery approach (spending longer amounts of time on fewer topics so you can really embed the learning) or stick with the spiral curriculum we've had since the numeracy strategy where you dot around all over the place, coming back to every topic each term but never spending long enough on anything (in my opinion) to actually learn it properly. Once you've decided that it will determine the direction you go in.
In my school we are using the White Rose Hub stuff as our long/medium term plans and then have several different books for teachers to dip into. So 1 copy per class of Maths No Problem (which I really love, but doesn't immediately seem to be that useful - when you get in to it, the way they explain concepts and the depth they go into is really impressive), 1 copy per class of the Collins Shanghai Maths workbooks and KS2 have Target Your Maths for times when they just need the children to work through some examples to embed a skill.
I absolutely hate, hate, hate, hate, hate Collins Busy Ant with a passion. A local school that invested in the latest version of Abacus is already coming away from it because it jumps around too much and they don't get long enough on anything. In my opinion, most schemes are just money making machines put together by publishers to make them the maximum amount of money by selling you as many different books as possible. You are far better getting a decent structure (both the White Rose Hub and Kangaroo Maths do this free of charge) and then spending what money you do have on resources for teachers to use with the class. As one of my colleagues said to me last year - give me an objective and pupil activities and then I can work out what I need to say to get them to the stage where they can complete the activities. But it's hunting down the activities that takes the time. So I would far rather spend the money on books for teachers/pupils so you've got good ideas of things for the children to do, than something like Abacus or Busy Ant that gives you a script to follow for the lesson. By the way, did I mention that I hate Busy Ant?
As you might have guessed from the length of this post, this is something I'm quite passionate about. I'm a Maths Specialist Teacher (MaST) and NCETM Primary Maths Mastery Specialist, as well as Maths Leader in my school so I've got lots of ideas and opinions about all areas of primary Maths!!