Gym day care

Okay so there's a new gym available in my area that offers childcare. I'm really considering signing up not only to work out, but to also help socialize my boys more. They're 3 and 1.5 and I've been a sahm their whole lives. They're only comfortable with a handful of people besides me and my husband, and only play with their cousins that they see regularly. They're superrrrr attached to me, which is fine, but I'd love to see them more open up a little and actually want to play with other kids.

Has anyone tried something like this and had any luck? Any tips on easing the transition? I was honestly planning on going just a few times a week but starting in small increments like 15-20 mins and increasing it each time.