For us, having three kids and no outside school means that sometimes I have to adapt an art activity for one or more of my girls so they can all join in. Making art and mess are things that both rate highly on the fun scale at our place and no matter what else is happening if I get the paints out I can be pretty sure all three will come running. Because there is around 2 years between each of my children there are some pretty big developmental differences-not to mention they each have their own way of liking to create!
6 year old Tannah is very organized and has clear ideas of what she is setting out to create
For 2 year old Harper it's more about the sensory play
Here are some strategies I use so that everyone is happy at messy art time.
-make sure everyone is in clothes that we don't mind get messy or put art smocks on. This means I can be focused on helping rather than caring about mess.
-SUPERVISE. Reminding myself here. It might only be 10 minutes before Harper loses interest but if I get distracted *ahemiphoneahem* She can upset the big girls by trying to "help" them with their art or get frustrated when I'm not close by to help. Not to mention paint the walls/floor/her hair.
-make sure there is enough equipment. Each child has a pair of scissors, a few paint brushes etc. Fights breaking out because there is only one of something is not fun for anyone.
-keep a much younger child at a separate table. For younger children messy art is mainly sensory so they will not pay attention to an older child's creation that they may have worked very hard on. It's not fair to expect a younger child to be aware or an older child to be understanding.
-don't compare artwork! Age is not the only difference. Personality, idea etc etc means that getting out the same materials does not mean similar results. Even in kids the same age. Comparing can be very discouraging-ask questions and make observations.
-if everyone finishes at the same time clean them up in order of age. The older the child the more understanding they will have of waiting and staying put. And remember everything can be cleaned! I'm a big fan of having a bath/wet cloths/towels etc ready to go beforehand if there is going to be a lot of mess
-don't assume that an activity is "too old" or "too young" for a particular child. Set it up and let them have a go if they want to. You might be surprised and they might surprise them selves by mastering something or really enjoying themselves.