i haven't gone to the trial lesson, but i have watched them once, i think still too young for the bb around 4-5months, coz most of the bb are 10-12 months. a little bit waste money to start at this stage
yes, i asked the same question with u, but when i visited their 4-6 months class, all the bb r around 10-12 months, if u bbcan't sit i recommend u can hold for this sem and wait until their next sem. of course business ma, they will sell u is OK ga for 4-6 months BB.
if you can buy a big gym ball at home, you can do most of the exercises that those gyms are offering for babies 4-6 months old. i've attended most of the professional/so called professional playgroups and gyms with my babies for her past 5mths. feel free to pm me for reference.