If its a genuine non-profit booster club (501-C3) then all contributions are tax deductible, and all contributions must be split between all members or "benefit" all members. No money can be used to benefit the gym itself - such as equipment, etc. Books must be open. comp fund stuff can be paid "through" the booster club (ie meet fees, coaches fees, warm ups etc) but not TO the booster club - as in members may personally donate $500 a year - and then that 500 dollars can be paid to the team comp fund/or meet fees, etc...BUT your $500 go to the booster club and each member gets their percentage - money can't be earmarked for individual kids...unless you vote as a booster club to pay Suzy's fees for Nationals, etc.
If its done right it can "feel" like you are paying $500 to your kids meet fees - but you are NOT and its a big point legally - because if another member doesn't contribute their $500 - the booster can't make them - there can be NO fees required. Your contribution, just like any money you help raise, has to go to ALL members.
If its done "wrong" its a big disaster legally, financially and inter-personally - it goes over very badly at one of my kids gyms when the booster "raises money for summer camps" which only certain families will attend no matter what....versus when money is raised to "off-set comp funds" that have been calculated for each and every team member to include all meet fees, coach fees, etc.
If the booster club is not a non-profit and not tax deductible I think they can do whatever they want - but the gym itself can be liable if equipment, etc is involved.
This is not specific to gymnastics, its specific to non-profits - my kids are involved in several other activities and I have been part of setting up several different strategies....so I do not speak only of opinion, but experience.