The walk from the marina to the centre of Cala D'or is uphill and a good 10 - 15 minute stroll. The taxis are very reliable and cheap though.
The Rocamarina does good entertainment but for adults only. That is on the opposite side of marina - nr Es Forti beach. My parents have stopped many times and enjoyed it there. The restaurant next to the beach/tennis courts are owned by the hotel but children are welcome there. They do lovely meals.
Sa Marina has entertainment nightly - childrens disco starts at 8 finished 9 - caters for english/dutch and german. Then adult entertainment afterwards - outside in summer months.
Tucan hotel always has good entertainment on when walking past but never actually gone it.
Also to get down to tropicana bar it's in a sort of 'dip' so it's steps either way to the approach.
Esmeralda Beach complex has a huge stage area and a lot more entertainment but that is further than the Tropicana bar.
I'd just have a walk around a few of the hotels and grab an entertainment schedule and see what you fancy on which night.
We normally do kiddy disco then venture off to Cala D'or centre, and watch the world go by - usually at Kalypso Tutti Frutti Cocktail bar - very laid back and children more than welcome. Also crazy golf in Cala D'or centre too.