No kids

Okay guys, your all wedding experts so I have a question for the experts. My good friend has a 5 yr old ish son. She and I have known each other for a long time as work best friends until she had to leave work because she was going to have her son. We've been keeping in touch online for may years and are both supportive of each other. She was elated with news of my upcoming wedding and I naturally invited her. Anyways, she knows that even though I love and support her, I am not the most child friendly person and have made it clear on my wedding website that kids are not the intended audience for this adult wedding. She asked me if she could bring her son. Right off the bat I want to say no because if I let her bring her kid, I hav to let everyone else bring their 8 kids and I'm out of room and money. My question is how do I say no without sounding like a shew beezy? She's still my friend and I would love to have her there, just without her kid. I know my request is controversial but in the end of the day, it's my wedding and I'm footing the whole bill and this is what I want. I even accept that she might not come without her son and that's sad but okay. How do I word no?