I speak to parents a lot about this, especially when they are heading into sleep or potty training. It can be stressful and counterproductive to your success, when you have a little one, or a few littles ones, and they are all signed up to different actives, at different times on different days; with you running around ragged trying to get them there.
Not forgetting, around these classes, you are also, feeding your baby/toddler and trying to fit in the sleep they need as well as things you need to do for yourself.
My go to line is: they have no expectations!!!! ONLY YOU DO. If you do not get to the park one day, or you miss a class - don't feel bad! You are the one setting that expectation and putting pressure on yourself, not them.
When children are young, they don't need to go to umpteen classes, they need good food, a calm environment and good sleep.
Now I'm not saying you should stay housebound, not at all, but what I am saying is, if you are are already finding things stressful, why add to that by giving yourself more things you need to do, or be at, with a huge diaper bag and stroller.
If you are at a class during your little ones nap time, believe me, they are not taking anything in, they are more likely going to be fussing and crying and thats not fun for you, you have to ask yourself is it worth it?
In my experience classes are always better off being attended AFTER you have a routine in place, and then you can find short classes around nap times, when your little one is more content.
As children get older, then signing them up for a few activities can be more fruitful and pleasant, busy toddlers need something to entertain them and get them out the house, but not to the point that they can not entertain themselves for an hour, if they were home.
I put a poll on facebook to see how many classes parents had their children in and what they were; you can see the results and thoughts here.
Personally I believe, swimming is the best class you can put a baby in - you can do a class or attend a drop in, with the pool being very flexible on times.
Swimming will also normalize their presence in the water so they are not fearful later on, swimming is a skill that could be life saving.