My name is T. I am a educational consultant for Discovery Toys. I love Discovery - their toys are very safe and all educational and very fun! They have not had a reacall in 30yrs. I would suggest the following toys from Discovery: I am not sure or your nephew's ability level, some of these are suggested for 4yrs and up, but my son who is almost 3 plays with these.
Busy Bugs #2109 (3yr and up) $17.99 - my son loves this it has bugs and lets the child sort match and practice patterns!
Playful Patterns #2930 (4yr and up) $19.99 - Shape recognition, creating patterns or matching shapes to make patters! This is a pogressive toy so he will be able to work the harder puzzles with practice but be able to do the easier ones now!
Inside out puzzle #2424 $17.99 (4yr and up) This is a wodden puzzle that changes from 2d to 3d. It has 24 woood pieces and is based on a Home theme. It has a car dog family and pieces that would fit into a home.
Bright Builders - #2290 (3 and up) $24.99 This has star-shaped connectable large sized pieces. The ends of the stars interlock three different way which makes building fun and easy!
Motor works - #2288 (4yrs and up) -29.99 My son loves this too. Although he has a little harder time if he takes them totally apart - I have to help him put them back together- Has a working battery operatd drill (triangular head to make it easy)the drill is used to take apart and put together the motorcycle, acecar and airplane - very colorful and cool. Once together the vehicles can be rolled around just like any other vehicle as the wheels move when the child pushes them. Oh it also comes in its own tool-box like carrying case!
There are lots of other toys to choose from Discovery these are just some of my favs for the little boys! Feel free to check them out: www.discoverytoyslink.com/rassega
if you have any questions or want to know more about some of the toys feel free to contact me and I will call you or give you my #.
Good luck - from a previous SE techer - buy him something that will challenge his mind. Often ADHD children are very bright and the more challenged they are the better they are able to focus. When bordem sets in that is when they tend to wonder off and loose interest- but don't we all.