Go for it! If I saw a 90 year old wearing a top made in that lovely fabric I would think, 'She has got STYLE!'
I generally think that everyone should wear whatever they like (as long as it's decent and not offensive), but I admit that I would cringe a little at anyone over 40 (30?) wearing cutesy baby-type designs (I think I would be wrong to, but I would!)
These flamingoes aren't cutesy - they're quirky and stylish.