I don't think you can ever get bored at DLR or WDW!
As far as days at each park, I would strongly suggest hoppers. Unlike WDW where the parks are far apart and hopping is a time investment, at DLR compared to WDW the parks feel like one big park. There is only a short plaza between them (less than the walk between where the bus drops you off and the gate at most WDW parks), and bag check is on the outside of the plaza so you do not even have to go through bag check to hop. We go back and forth all day. It literally usually takes 5 minutes to get out of one park and into the other. We have been from the back corner of DL to the back corner of CA in 10 minutes! It is very convenient, if say the lines seems really long in the afternoon at DL, to hop over to CA where there are shorter lines. It is very convenient if you want to see the fireworks from inside DL, but they were cancelled one night, to hop over from CA the next night and catch them. One night last July, we saw WOC at CA our first full day, and then on a whim hopped over to see if we could catch the late Paint the Night parade at DL- found a fantastic spot- and then our 2nd night when we had it planned we didn't have to worry about trying to stake out a spot for it (although we loved it so much- that we found a spot for the 2nd showing anyway- but there was no pressure or stress). Also, at least in the summer, DL usually has later hours than WOC, so we sometimes stay at WOC until closing, and then hope over to DL until they close. Hoppers are definitely worth it for DLR!