The groom is trying his best to accommodate his sister while still honoring his fiancée's wishes for a child-free wedding. He has even offered solutions like arranging a playroom and finding a babysitter. It's unfair to expect him to completely upend his wedding plans. The sister should understand and respect the couple's decision for their special day, especially given that she knew about the wedding plans well in advance. It's not the groom's responsibility to solve her childcare issues.
The groom claims to be accommodating, but he clearly prioritizes his fiancée's desires over his own family. Announcing the 'no kids' rule only a week before the wedding is a deliberate move to box his sister into a corner. Offering a playroom where the sister and other family members must take turns supervising is hardly a gracious solution. It reeks of insincerity and a thinly veiled attempt to avoid genuine compromise. The groom is selfishly putting his sister in an impossible situation.
The groom made efforts to accommodate his sister by suggesting a playroom and a babysitter, indicating some willingness to compromise. However, the late announcement of the 'no kids' rule placed undue pressure on the sister, especially considering the long travel distance. The sister also bears responsibility for assuming her children would be welcome despite the couple's preferences. The situation could have been avoided with earlier and clearer communication.