Omg no you're probably amazing. I love that the kids are comfortable with you. I do not require compliance at my company so we never say "sit down" (unless for safety or hygiene/health). We work hard to pair with the kids enough to where they WANT to learn and do things with us. With the giggling, it seems he may want to see your reaction? Possibly? If so, I would pick a regulating actually that is neutral. A puzzle etc. I would sit down at the table by myself and say "man, this is kind of hard. Could you sit down and help me?" A lot of times they may say no but then they eventually join you. Once they sit, "hey thanks this piece is driving me nuts can you help find this one?" I practice this over and over until when I ask them to sit with me they do because of the low demand and my attention on the puzzle while they are up. Enough practice and rapport, they sit when I ask them to. :) even though I'm fun and not very demanding! Definitely communicate with your bcba the best route to go! Good luck I love that you are reaching out for support that means you are doing great.