It is sexist (but, yes, more in extremely bad taste and juvenile in the extreme, and unprofessional) because it further contributes to the hostile environment in the tech world. It says "NO GURLS ALLOWED. HYUCK, HYUCK. YOU HAVE TITTIES AND COOTIES" to any woman who is interested in working in tech. If that is not the intended message, then I suggest some of these emotionally 12yo gomers talk to some marketing people about branding and crafting their message.
If this is the only way you know how to do business or to demonstrate a project or idea, then you need to go home and grow the hell up
And here's the thing -- I am visibly 60, dress very conservatively, and will still have my breasts "accidentally" groped and stared at. I am not responsible for the actions of others, including those who will not see me as a person. It is not my job to make these sorts of men behave like adult humans in a business environment, And, yeah, it should be safe (if boring) to take a 9 yr old to a business conference. There should be nothing there, unless it is a medical application, that should be inappropriate for him or her to see. If there is, you are doing it wrong. Write your fake apology in advance.
It would be easier to take this as ironic if this were not the same as the rest of the toxic stew that women who want to work in tech swim in daily.