I can't answer this question, but perhaps can offer some info:
Edit: I realized that what appears below would perhaps be more suitable as an answer to a question like: "How do you cope with the reality of being at an undergraduate-focused school when you had your heart set on a research career?" This is markedly different from the OP's question, but evidently my answer seems useful for this one. Perhaps I've implicitly answered the question...It would be nice if this question received an actual explicit answer! (e.g. I think Joseph O'Rourke's deleted answer was closer to the mark than mine is!)
1) Not all liberal arts schools are the same. Not considering the elite schools, some departments have 3 hour loads distributed over two courses. I work at such a place. Office hours and service are still more of a commitment than at a research school, but there is still time left over to work. My college is clearly trying to raise its research profile a little. My feeling is that due to the sheer number of qualified PhDs looking for jobs this is an emerging market, and so colleges that want to move up in the rankings will consider reducing teaching loads in order to take advantage of the oversupply of strong research candidates. You won't be able to write two good papers per year...perhaps not even one good paper per year...but you will be able to do research at such a place. Chances are, if you have tenure at a small school then you have a knack for engaging undergraduates (whether you like it or not). I'll bet you will be an attractive candidate for a move to such a department.
2) This is presumptuous to write, because it's pretty obvious, but getting a good research job usually requires making very serious sacrifices. Many of my research friends still are working hard on work/life balance issues. Some have had to be separated from a spouse (often on a different continent) in order to try to get a decent research job. I can't help but think that people who land these jobs often quite deserve them. I can say that my own unwillingness to expose myself to such risk is the main reason why I originally accepted a job at a liberal arts college instead of trying to go to a research university.
3) Having just chaired a search committee, I've recently reviewed more than 750 applications for a tenure-track liberal arts job. The gut-wrenching truth is that there were more excellent research candidates than the market can support. If we restrict our attention only to those with at least one postdoc, it is probably possible to fill all openings on MathJobs with candidates having more than 5 publications (and this is conservative). Budgets allow for bringing a few candidates to campus for an interview, and almost nothing is worse for a potential employer than blowing a campus interview on someone who is not serious about a position. To some extent, your vulnerability as an applicant is attractive to the interviewer. If you have tenure already, it is possible that you will be harder to secure...or worse, will be seen as collecting offers to bargain for a raise at your current job. Unfortunately, I have strong evidence that this happens. In one case, this evidence stopped us from talking to an untenured candidate. I think that this is the main reason why it is nearly impossible to move after tenure. (Sorry to kill hope...I hope I am wrong about this!)
4) One final important point I forgot to include before. As you mourn the fact that you never will teach graduate courses or supervise PhD students, keep in mind that there is an important positive side to this fact: You will not have to help such PhD students find an academic job in the current market. I imagine that having taken a job at an undergraduate institution, if you were to relocate to a more research-based position it probably will not be Princeton. Instead, you will probably find yourself at a lower-tier research school. I speculate that PhD students graduating from such schools are at a disadvantage for landing excellent postdocs (If I'm wrong about this, someone please contradict me) and subsequently finding permanent academic employment. I imagine watching students go through this would be very stressful for a conscientious thesis advisor.