Also, as you NEED bigger units, read the Last Minute Rental thread regularly. For the $100 per night weekly limit, you can visit 2bdr units for way lower than the MFs most of the time.
When looking to buy ... you must now consider SCHOOL schedules. And most likely you will be driving. Your Home Resort will save you money by not paying exchange fees and will allow 'brainless' vacations. Yee ... a summer vacation either week 26 or 27 is usually July 4th week ... buying that week in the mountains or on the beach; same for other weeks for different time of the year and school schedules. Might cost you MORE than a cheap offseason week to buy ... but you will have save lots of time and planning. And kids generally, like knowing where they are going.
If you listen to PRESENTATIONs by timeshare sales people, they will LIE about easy trading into PRIME time or trading up in seasonal stays at the resort (as an owner). Remember, each resort usually sells 51 out of the 52 condo weeks per unit - the 52nd week (not "week 52") for maintenance or out of service. You need to buy WHAT you use.
Also, buying into 3 different 'systems', means learning 3 totally different sets of "RULES". Rent and ask lots of questions before buying. I own Wyndham points plus Fixed Weeks at a separate (non-Wyndham) resort. Planned as the resorts are in the same area (6 miles apart) ... I just drive down the A1A/Ocean Drive when staying in the area (in the dead of winter).
Way easier to buy than to sell ... so research and figure out YOUR plan before buying ANYTHING. Buying is easy ... selling is WAY harder.