Unless it's an all day thing, I wouldn't bother. We didn't arrange anything for the little ones at my 30th or my dad 70th nor have I seen things set up for kids at any of the other parties we've been (huge family, lots of kids and lots of parties). There's generally a disco and the kids are very happy dancing / sliding across around the dance floor. And if they're anything like the kids in my family you will need to prise them away from the photo booth! But if you really have your mind set, how about some colouring books and crayons for the younger ones and some board games for the older kids. If you have space at your venue and it's spring / summer time you could hire a bouncy castle (just beware of drunk adults getting on it, especially if kids are still on there)
One of the best weddings I ever went to had a Rock Band room. Someone took their XBox and a set of the Rock Band games, with the instruments - two guitars, microphone and drum kit. It was a great ice breaker, everyone loved a singalong and watching the mum of bride and mum of groom blasting out Blondie while accompanied by the groom’s 80 year old grandmother who it turned out had always wanted to try playing the drums was one of the most memorable moments of the wedding for me.
You can hire giant scaletrix tracks that get set up for you. We had one at our wedding and it was very popular with kids and adults alike. It had about 6 or 8 lanes so several people could play at once. It's also possible to hire table football.
We also stuck stickers of about 15 different Disney characters around the venue. E.g. One on a toilet door, another on the buffet table, another on the coat racks etc... The kids competed to see who could find and write down the names of all 15 first. It took them a while!
Print off some personalised Mad Libs sheets for guests to fill in anonymously!
I lkke these games. Depending on how many people you have.
-Poop the potato -Pegs on collars/clothes the one who manages to nab the most pegs from others by the end of the night wins a prize -treasure hunt- card/10 questions (about you?) with the info hidden round the party in boxes with mini prizes like Haribo. Small kids look for treasure boxes, bigger kids do quiz