Bad:
Biscuits too freely available at Group 2, I have to distract DS from them.
Only fruit offered at Group 3. DS3 doesn't eat fruit. (He will feed fruit to me, but won't try it himself). I have to remember to bring cheese crackers for him or he gets very grumpy and hungry at that group.
Group 2: Bad layout: the seating is in a long line, so parents have to be careful to sit down to someone you don't mind talking to an AWFUL lot, or you end up sitting on the floor by yourself, or standing around just to find someone to chat to.
Bad: any group that leaves the biscuits/snacks in plain sight the whole time. MY DC will clamour for them the whole time we're there if they're visible like that.
Good: Group 1 has clumps of chairs in different parts of the room. There are crafts/general toys out, with a sit-down snack of fruit/savory biscuits/sweet bix, then all that cleared away and the ride-on toys come out for 20-25 minutes. Long ago, my favourite group had ride on toys out the whole time, but you need a quite big room for that to work.
Good toys: Brio train track, Duplo, some dressing up kit, Kitchen (as stated), tunnels, garage and cars and playmat to push them around on.
Can end with parachute games rather than just songs.