Travelling on your own can be tiring but it's great too. My ds (11) tells me some of the best times we've had have been on holiday, especially those that are just us.
I highly recommend PGL, though you're two will be too young for a while. There were several single parents as well as two parent familys, and one group had brought grandparents too! Do loko at their familt holiays when your two are old enough to go.
Have done mango (in the UK). Was great fun, my ds loved it, but can be rather pricey. You are paying for the company of other adults and friends for your dc's at the end of the day. I would do it again but I can't afford their foreign destination prices.
Centre parcs is another great place for a few days away. Might be more tricky with two young ones on your own, but they have creche facilities and babysitters so you may want to wait till their a little older and perhaps do some swimming activities with one while other in creche for example, then swap.
My sister told me it would be her idea of hell when I suggested we go away on holiday together, even when I offered to pay for us all. She also tells me that she wants to spend time with her husband and kids alone, despite me offering to babysit so they could have time in the evenings together etc. I don't bother asking her any more needless to say.
It is tough on your own, but it's also great fun. You just have to plan.
ps don't necessarily think package when you go away, single adult with dc are way to expensive on a package usually. When we went to New Zealand and California (which I did a few times when ds was younger) I always book everything separately. Hotels in USA are charged at a room rate regarless of how many in there, so no single person suppliment if you book yourself!