It’s hard to say what is the “appropriate” amount of worry– It is good that this will be assessed by a vet. It is very important that recently neutered/spayed rabbits are in a restricted space to ensure no complications in recovery. While the rabbits may start a fuss, restricting their movement/jumping/running abilities is necessary, just like going through the stress of nail clipping or grooming. You can put a ceiling over the pen to prevent jumping, as well as cover the outside so there are no visual cues to facilitate an urge to escape: https://wabbitwiki.com/wiki/Training_FAQ#My_rabbit_keeps_me_up_by_consistently_chewing_his_cage_bars._How_do_I_make_him_stop.3F .. A bedsheet nicely clipped, end to end (no gaps or holes peeping through), can provide enough visual cue that most rabbits will not try to jump into it.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.