I have two very simple messy play materials that both babies and toddlers will love!!!!
Shaving foam is the first one; I just brought some cheap shaving foam, put it all over the tray and then let them get stuck in (please excuse the stained tray, that was from another messy play!).
The other one takes slightly longer to prepare but is just as fun; just mix cornflour and water together. Make sure you don't add too much water as you want a really gloopy substance so that, when you touch it, the warmth of your hands makes it slightly more liquidly (Chris was amazed by this as it is also very relaxing to play with!!!).
Generally the tidy up was alright but you do still get a bit of mess (I don't think it is possible to avoid this with a toddler)!
Let me know if you do any of these activities and if you have any more messy play ideas.
Love Sophia xxx