kids clubs included for kids over 3. after a certain time (i think 10 or 11 pm) there is a charge. i think it's $7/hour. for kids under 3, some ships have a nursery (i think oasis does) but you have to stay with your kid. they also offer in-room babysitting for a larger fee ($15 or $20/hour, i think).
there is food 24/7. promenade cafe is 24/7, sorrento's (pizza place) is open until 3 or 4 a.m.
room service is 24/7. from midnight - early a.m. (i think 5) there is a $4 or $5 flat fee delivery charge. other times, no delivery charge, though we do always tip whoever drops it off.
tap water, flavored water, iced tea, lemonade, milk, chocolate milk, regular hot tea and coffee are included, and powdered hot chocolate mix at the cafe promenade. juices in the a.m. also, though not fresh-squeezed. soda is not included, but you can get a soda package for $8/day, or just buy as you go (i think $3 each or so). upgraded coffee (like starbucks, frappucinos, etc) is not included, nor are virgin cocktails. these run about $5 each, or you can get a package called royal replenish that includes soda, virgin cocktails, fresh squeezed oj, frou frou coffee/tea/hot chocolate, and bottled water for $22/day.
tons of included restaurants, as noted above by others.
no charge for most actvities - flowrider, rock wall, zip line, carousel, mini golf, ice skating, etc. you can purchase private time/lessons on the flowrider if you want.
the only real on-board purchasing difference i've seen between disney and royal is the lack of free soda. pretty much everything else you get charged for on royal, you'd also get charged for on disney - spa, bingo, excursions, tips, etc. royal also has a casino which of course charges.
re the towels, it's to stop the chair hogs from placing a towel on a chair at 7 a.m. and never coming back for it. if they have to return it, they will come back and get their towel! the no return fee is $25, and trust me, the scratchy cheapo towel is not worth that! fwiw, i've never seen a line at the towel cabinets, but if you're concerned, just get a bunch at the beginning of the cruise and keep them in your room, or if you'll need them for an excursion just get them the day before. randomly, if you're in a suite your steward can get them for you and they won't be "checked out" so you don't have to worry about charges.