C.M.
What about some fun outdoor toys that include water? Water guns, sprinklers, etc?
Also, I'd suggest (if you aren't already doing this) putting toys into boxes of some sort and only taking a few out at a time. Then rotate them with the other boxes every few months. Chances are that maybe he has TOO many toys to play with so he becomes overwhelmed and then doesn't want to play with anything.
My brother has a 4.5 year old and they do this (rotating toys) and he said it's almost like Christmas when they rotate because his son has forgotten he ever had those toys!
As far an entertaining him while you clean or get dinner ready, I suggest:
While you are cleaning: Have him help - give him a wet rag and have him wipe down the counters, floors, sinks, etc. Give him shaving cream and put him in the tub (clothed or naked, water or no water) and let him play with it on the shower/bath walls. Have a bin of stickers and construction paper and let him do that while in the same room with you. Give him a bag or box of misc toys and have him sort them by color, shape, size, etc.
While you are making dinner: Give him something to do - set the table, empty the dishwasher, let him play with playdo, let him make his own pizzas (on english muffins), ask him to 'organize' the tupperware (ie: play with it), let him 'wash' dishes - my daughter loves this one! paints and coloring are also things my daughter does while I'm trying to keep her busy while I'm busy.
If all else fails, I do use the tv - sometimes I think it's okay to have a distraction so I can do what needs to get done!