How can I get monster in law to realize that she doesn't get to make decisions for our children?

My 2 YO starts dance cles next week and my moster-in-law pitched a **** fit when my hubby was casually talking about it to some people while she was sitting there. She thinks it's rediculous that our 2 YO is dancing and that it is pointless and that she should be doing something else. I danced from 2 until I was 16 and LOVED it. It's not overly expensive, is on sat mornings for 45 mins and is a cl of all 2-3 YO's, a few of whome my daughter plays with regularly. She's not getting covered in makeup and forced to dance for hours on end. It's just for fun and socialization and if she likes it she can keep it up, and if not she can stop. There is a recital that she isn't required to b in if I think she'll be too scared. My MIL thinks I should wait until she is older and have her play softball (not at ALL my thing...but SUPRISE MIL used to play and coach!!!) Wonder why she chose that. It's a cutesy fun thing for her and she is sooo excited. But my MIL is already saying to our 2 YO that she won't like it, and it's stupid. That it's sooo scarey on the stage and blah blah blah trying to overtake her opinions. Any advice?