You have four choices: You can welcome children with open arms; you can decide to have an "adults only" wedding; you can include immediate family only; or, you can hire a child care service to provide day care either at the reception space, in a hotel room or at a family member's home. To prevent hurt feelings, it's wise to avoid allowing some families to bring children while excluding others (unless, of course, the children are in your bridal party).
When it comes to bartenders and waitstaff, and parking, bathroom and coatroom attendants, the rules of tipping are dictated by your contract. If the service fee is included, consider doling out extra only if the service was exceptional. If it's not included, ask ahead of time how many attendants will be working your wedding and calculate on a per person basis.