Hi Rebecca,
The Hotel Levante in Cala Bona (East Coast) is excellent. The Levante is right on the beach but with a private swimming pool. Its a Thomson Gold hotel so there is entertainment every night if you want it and its adults only so no under 16's. You can also use the Levante Park's facilities, which is its sister hotel across the road. The food is absolutely fantastic. There are a couple of other posts about the hotel, and no doubt reviews on it as well. Its definitely not an 18-30 hotel, you will find that the majority of (but not all) the guests are probably 40+. However it is definitely safe, and extremely convenient for the beach and the resort itself.
I've not stayed myself but have heard that the Hotel Moreyo is clean, cheap and good value as well. I also know a couple of people who have stayed at the Hotel Cala Bona and that is also very good but overlooks the harbour rather than the beach.
There are loads of bars, cafe's etc... in Cala Bona itself and its only 10-15 minutes walk down to Cala Millor which is a bit livelier.
Louise