The subject of how to address an "adults only" shower or wedding has come up time and time again. Tradition (and proper addressing etiquette) dictates that only those whose names appear on the envelope are invited. Do NOT have "adults only" printed on ANY invitation, whether it is for the bridal shower or wedding! There are much more eloquent ways of handling this sometimes delicate situation.
Some of my customers that are planning a black tie affair or a rather large wedding celebration are quite insistent on verbalizing their wishes on the RECEPTION CARD, which is included with the formal wedding invitation. I recommend to print "Adult Reception" on the reception card (NOT THE INVITATION), and then proceed to give all the details such as the place, address and time.
Although this is acceptable, I prefer to bypass it completely and to address the invitation envelope only to the intended invitee(s). The inner envelope of a formal wedding invitation is where you directly spell out that specific information. For instance, if you are inviting Mr. and Mrs. John Jones, Jr., that information will be written on the outer envelope. Jessica and John will be addressed on the inner envelope. This should make it very clear that two year old Johnny will be needing a sitter for the evening.
However, please be prepared to explain your wishes to parents who inquire. You can explain to them that although you and your fiance have many special little ones in your extended family, you have decided to have an "adults only" reception. Most of your friends and family will understand this and will hopefully look forward to an adult evening. Be firm. If you allow one you may offend others. For those that do not accept your wishes, they can choose to politely decline.
Additionally, keep in mind that if you have MANY family members or friends with children that live out-of-state or country, you may have to make special accommodations if you want all adults. Some parents will not feel comfortable leaving their little darlings behind and may have no other alternative. One idea is to hire a competent caretaker to watch them at a nearby relative's home. Another option is to have the babysitter at the reception facility in another small room. Although this last idea may work in some smaller and more casual settings, it is more of a hassle and financial burden in my opinion. Most of the larger banquet facilities in the south jersey region do not make provisions for this type of situation. It may take extra planning on your part to make everyone happy and comfortable.
Remember, this is your wedding. Good luck with your planning!