We went last May with our two kids (10 and 6 months), I always felt in security. They cooed and talked to my baby the whole ride (we went to Tulum, Playa Del Carmen and Xcaret with the collectivos). Only thing that might change your mind is that the collectivos are a fee per person, the taxi is for the bunch so sometimes it's not worth it. We carried Penelope (6 months) in a baby carrier (ErgoBaby). Honestly going with kids was one of the best experiences we've had. The Mexicans are SO great with kids! I'm still breastfeeding and they always smiled at me, even coming to talk to her while she was on my breast. So great! My 10 year old enjoyed Xcaret, we didn't try the other ones as we didn't have anyone to watch Penelope. I'll get back to you for Tulum, I can't remember, I'll have to ask FI.