Great question! Here is a thorough breakdown of our boys’ products to help you find the right size!
If the boys you're shopping for are ages 1-5, we have boy's clip-on bow ties available here!: https://www.thetiebar.com/bow-ties?type=boys-clip-on
Any age 6+ should be able to wear our pre-tied or self tie bow ties! These will have an adjustable clasp that can be worn with neck sizes 13 3/4" to 18 1/2", so as long as they're within that range, that will be a good fit! If you're worried about them fussing with the bow, I would suggest the pre-tied option so that it doesn't come undone.
Our boy’s neckties are 48 inches in length - meant for boys aged 8-13, or between approx. 4-5 feet tall. You can view boy’s neckties here: https://www.thetiebar.com/ties?length=48-inch
That being said, necktie length can easily be adjusted by tying the tie unevenly (so that it ends up the correct length) and trimming or tucking the tail end of the tie.
As for suspenders, that really depends on their height. We have two options for Boy's Suspenders here, that adjust from 20.5" to 34.5". These are meant for approximately ages 1-4: https://www.thetiebar.com/search?searchKey=boy%27s+suspenders
Otherwise, our men's suspenders adjust from 29" - 46", so I would recommend measuring their torsos to see which ones would be a good fit!
We have 2 options for boy’s socks, for toddlers approximately 2-4 years old. (specifically shoe size 7.5-12 for Toddler Size Shoes). You can view those here: https://www.thetiebar.com/socks?type=boys