My preference is for adults only, but i do have friends that have young kids.
It was helpful to hear about the secrets experience as it is something I will have to keep in mine for guest who would be coming solo
I was in a wedding where we stayed at the resort and it was beautiful. The bride actually had the wedding off resort but the beach wedding I saw were nice
One caution I would make is that if you invite these additional people to the wedding, then you will need to have some process in place to ensure that they do not follow to the reception. Maybe you will have to have someone to sign guest in.